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5E Spellcasting Rules Conversion

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This mod is a major rules conversion, allowing all normal 'Vancian' spellcasters (mages, bards, clerics, druids, etc.) to use the more flexible rules found in 5th Edition D&D.

Download the mod over here.

Check out the Readme over here.  I'll replicate most of the Readme in this post, at least as it exists now (version 0.6). Please do read the readme fully - it has important, detailed explanation not just of what this mod does in the game, but also some of the limitations of the mod and other mods that you can install that work hand-in-hand with this one to overcome those limitations.


This mod has an ambitious scope: to change the fundamental spellcasting mechanism for almost all spellcasters in the game. The short description is, it makes the game use D&D 5E rules for how spell slots work.

For a proper, longer explanation, let's start with a brief run-down of spellcasting in BG games. You can know spells, and you can memorize spells, and you can cast spells. In the old AD&D 2E rules, which the BG games use, your known spells are one thing, but the spells you memorize and the spells you can cast are identical - memorize Magic Missile twice, and you can cast Magic Missile twice. Contrast with sorcerers: their known spells and the spells they can cast are identical, but there is no memorization. If you have two 1st-level casting slots, then you can cast any of your known 1st-level spells as many as two times. (This mod does not change sorcerers at all, I'm just mentioning them to tease out the way these systems work.)

The D&D 5E system separates memorized spells from spellcasting slots, and ends up as a bit of a hybrid system between 2E mages and sorcerers. You have a certain number of memorization slots that allow you to 'prepare' spells for the next day; then, the next day, you can cast any of those prepared spells like a sorcerer. If you prepare Magic Missile and Shield, and you cast Magic Missile, you do not lose your only Magic Missile spell; you still have a 1st-level casting slot and you can still use it to cast either Shield or Magic Missile. So you can learn and memorize spells like a mage, and them cast them spontaneously like a sorcerer.

If you think this gives mages a serious boost compared to sorcerers, you are not wrong. It does level the playing field to an extent. But sorcerers still pack more brute power. They have more casting slots then these 5E wizards - this 5E system gives mages the same number of casting slots as Dragon Disciples, i.e. one fewer than a sorcerer at any given level. So sorcerers can still just cast more spells and power their way through a situation.

(NOTE: I've been talking about wizards and sorcerers, but this mod affects all traditional spellcasters: mages, bards, clerics, druids, paladins, and rangers. At some point I may split these up and allow the changes to be made for some classes but not others... but for now this is an all-or-nothing total rules conversion.)

As for the mechanics of how this works: you have to be a bit more intentional in playing spellcasters. During the normal course of things, you will not have access to your spellbook. In order to prepare spells - either because you want to change your prepared spells or because you have leveled up and can prepare more spells - you need to intentionally open the spellbook right before you rest. In-game, the way you do this is by activating an innate ability called 'Change Prepared Spells.' This will disable your spellcasting until you rest, but will give you access to your memorization slots. Fill the slots with whatever spells you want to prepare, just like in normal gameplay, and then rest. When you wake up, wait for 1-3 seconds and you will see your spellcasting button go dark and then light up again. Now you no longer have access to your memorization slots, but you can spontaneously cast any of your prepared spells.

You don't have to use the 'Change Prepared Spells' button every time you rest. If you are happy with the spells you have prepared, then you can simply cast them and rest, cast them and rest - gameplay will be a lot like with a sorcerer. The innate ability is there for when you learn new spells or would like to prepare different spells for this or that dungeon, or whatever.

Limitations: this system very faithfully recreates the method sorcerers use for spellcasting in the game, but I'm at a bit of a disadvantage since they are hard-coded and this is just a mod. There are several limitations involved in this spellcasting system.

  • 5E Spellcasters cannot use the traditional 'Identify' spell. That spell is hard-coded to work in the inventory screen. As a workaround, this mod installs a small UI tweak and a new Identify spell yhat you cast from the main game screen, instead of using in the inventory. A small bonus: now the spell gets better as you level up, allowing you to identify up to four items with one casting.

  • 5E spellcasters cannot use traditional Contingency or Spell Sequencer spells. This is due to how they are hard-coded to work. To address this, the mod will modify these spells, allowing you to choose from any known spells, instead of any memorized spells. A side-effect of this is that they will not longer exhaust memorized spells (for any casters of any type) when this is done.

  • 5E spellcasters cannot use quickspell slots on the main UI screen. They are hard-coded to function in a way that doesn't work with this system. There is no workaround for this one... sorry. It is an inconvenience, but not a huge one. Several spellcasting classes don't even have quickspell buttons in their UI. Hopefully the added utility and flexibility of this spellcasting system more than make up for the small UI limitation.

  • The last limitation has to do with items that increase your spellcasting slots, like the Ring of Wizardry. In the base game these increase both memorization slots and casting slots for mages (since those are identical for mages), and increase casting slots for sorcerers. Here, I faced the question of how they should work: should they increase your memorization slots (for more flexibility), or increaser your casting slots (for more power, like sorcerers), or both? If a 5E caster wears an unmodded Ring of Wizardry, it will only increase their meorization slots. But most people like increasing their casting slots, so there is a secondary component in this mod that will change those items to do that. The caveat is, such items can only add one casting slot per spell level. So for example, BG2's Ring of Acuity usually gives you two bonus 2nd-level slots... not it will only give you one. However you can combine different item to get multiple +1 bonuses. For special items that double your spell slots like BG1's Evermemory ring and IWD's Kontik's Ring of Wizardry, this mod will give them an active item ability to refresh your spell slots of the appropriate spell level, instead of having the passive effect of adding memorization slots. Use that ability once per day, and you've doubled your casting slots. So the original design is replicated, just in a different way.

If you are going to use this mod, do not install the 'Revised Specialists' component of Tome & Blood. That component allows specialist mages to spontaneously cast spells in their chosen school, but the mechanism is clunky; this mod lets mages cast any prepared spells spontaneously, and it gives a particular bonus to specialists: they can cast any spell in their chosen school without having to prepare them. They lose one memorization slot per level in exchange, but they will have more than one spell in their specialty at most levels, so it is a net gain. (I particularly recommend the 'Rebalance Spell Schools' component on Tome & Blood in conjunction with this, since it makes sure that there are two or more spells from each school at each spell level. Not to mention mods that add more spells, like Spell Revisions and SCS or IWDification.) Tome & Blood's Revised Specialists component adds other advantages to specialists, which you will have to do without... I am working to add support for those changes.

This should be compatible with other mods that affect spells and spellcasting. For example it should work with Tome & Blood's 'Revised Invisibility' and 'Revised Illusionary Clones,' and I have gone to great lengths to make sure it is compatible with all aspects of the Faiths & Powers mod. (Only note, F&P has an option to add sorcerer-style casting to all priests... I would use that option or this mod - not both.) This will work with the 'Ability Score-Based Bonus Spells component that is in both Tome & Blood and Scales of Balance... your best bet is to install that via Scales of Balance, after both TnB and this mod.

I have specifically excluded spellcasters from AionZ's 'Shadow Magic' mod from these changes, since thye use different spells and different mechanisms with which I am not familiar.

These changes only affect characters who are in the PC's party - enemy spellcasters should be untouched. Getting computer-controlled casters to handle changes like this would be a near-impossible task. By leaving them alone, we let you install an AI mod like SCS and it will work optimally, continuing to improve that aspect of gameplay.

This mod should be installed after mods that add spells to the game, like Spell Revisions, IWDification, and SCS IWD Spells. It should be installed after Tome & Blood and Faiths & Powers; but before Might & Guile and Faiths & Powers Multiclass.

The mod converts any arcane spells that have a scroll from which you can learn - since it changes the spellcasting method of casters who learn spells from scrolls. On the divine side of things, it will convert any spell that is typically available to clerics - that is, any spell with a 'SPPR' prefix and numbered from 101 to 150, 201 to 250, etc. Notably, this excludes divine spells that are added by mods that don't use the traditional naming structure and apply them via a UI hack. At the moment there is no way for me to effectively find and capture such spells. If you use the Faiths & Powers sphere system, then this mod will convert all divine spells in that sphere system, instead of using the traditional method.

Edited by subtledoctor
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Here is a video of how it works, starting with how the spellcasting system is initialized at the beginning of the game, and showing how you can cast spells like a sorcerer and then change out your prepared spells.


A word about the beginning of the game:

For Charname, this generally works fine. You will memorize a bunch of spells in the character creation process (don't double up! Memorize one of each, remember you can use all your casting slots for any spell once gameplay begins), and when the game starts you will see your 'cast spell' button wink out and then be enabled again.  You are good to go.

But things get a bit complicated with NPCs, and with other mods. I am currently playing a game with Faiths & Powers, and NPC_EE changing the class of some NPCs and setting them to level 1, and Tweaks Anthology's 'TOB-Style NPCs' which uses the lowest-level versions of various NPCs and then bumps their XP when they join the party. Here's what happened with Jaheira:

Faiths & Powers strips divine-class NPCs of known and memorized spells, and then fills their spellbook with spells from their spheres, and gives them an innate ability that turns the 'dim,' unmemorized spells  in their spellbook into memorized spells that they can cast. I set Jaheira to level 1 with NPC_EE.

Before I released Jaheira from her cell in Chateau Irenicus, I saved the game. (Save your game when doing things like recruiting NPCs!) She joined my party, my dog-slow iPad got bogged down for a few seconds as some scripts ran, and my attention wandered. I went to the Record screen and leveled her up and only afterward did I realize that she had no spells to cast.

So I loaded from that savegame and did the following:

  • I immediately paused the game when she joined the party. I went to the Record screen. Jaheira was level 1, with 89,000 XP. I leveled her up.
  • Then I went to the priest spellbook screen. I set various spells to be memorized.
  • Then I went to the game screen, with the game still paused.
  • I used the Faiths & Powers 'memorize spells' innate ability which has an annoying long casting time and I should change that.
  • A second or so later, the game scripts converted Jaheira to this 5E spellcasting system, and her memorized spells became available to cast.
  • A second or so after that, Tweaks Anthology bumped her XP to 160,000 and she could level up again.

The 5E conversion is very likely going to happen before the Tweaks Anthology XP bump kicks in; and if you use SCS 'NPC Customization' component, its XP-bumping scripts will probably be too slow as well. But with NPC_EE or Level1NPCs, and with some quick game-pausing and preparing her spells, I was able to have her casting like a champ through the initial dungeon. The same procedure works for Imoen, and for other NPCs whose spells you want available immediately after recruiting them, like Aerie.

If you are using SCS NPC customization, or you just don't want to deal with quickly pausing the game, your other alternative is to use the NPC's 'change prepared spells' ability to set up spells to memorize in their spellbook, and then simply rest. After sleeping you'll be able to cast their spells.

Edited by subtledoctor
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23 minutes ago, Endarire said:

How does it work with multiclass casters like Mage/Clerics or Cleric/Rangers?

Just fine. As in the vanilla game, cleric/rangers will get casting slots according to their cleric level - you get the higher of the two values for your divine casting slots, not a combination.

25 minutes ago, Endarire said:

Do the quickslots work with the newest EEex?  Bubb revised that recently.

Don't know. I can't use EEex, so I can't code for it or test it. (Nor would I want to write code that only works on games I can't play.)

If anyone wants to take it upon themselves to write an add-on mod, via UI hacks or EEex, to allow quickslots to work with this system, by all means go right ahead. It's not too complicated in concept - you just need to allow quickslots to cast innate abilities. Innate abilities are deemed "memorized spells" in the .CRE file, just like divine and arcane spells... so I assume they are accessible.

For me, it's just not a big deal. Plenty  of casters don't have quickspell slots, and I barely even notice in-game. Like, I couldn't tell you right now which classes have quickspell slots and which ones don't. And I've never said to myself "I'm not allowing Jan  in my party this time, because mage/thieves don't have quickspell slots and I must have quickspells!" (YMMV of course...)

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To my present understanding, the latest EEex already allows innates to be quickslotted.  If so, Bubb pre-solved your problem!  Alleluia!

Also, to clarify, how do multiclass spontaneous casters (like Sor/Druid) work with this sytem?  I assumed they worked well, but I wanted confirmation.

Does this include any of the spell ID reworking to work with OlvynSpells?


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3 hours ago, Endarire said:

how do multiclass spontaneous casters (like Sor/Druid) work with this sytem?

Hm. I didn't get around to testing those together. I would imagine that they have the same issue as when you used the former versions of TnB and FnP to make a spontaneous caster on both sides - it will work fine, but the order of spells as they appear under the 'cast spell' button will shift from divine-arcane to arcane-divine, depending on which kind of spell you cast most recently. I can probably make that stable, when I get around to it.

3 hours ago, Endarire said:

Does this include any of the spell ID reworking to work with OlvynSpells?

It's addressed in the readme, but: arcane spells are pulled into this system based on whether there is a scroll from which you can learn them. (Because the system affects spellcasters who learn spells from scrolls.) So if Olvyn's mod includes scrolls for the arcane spells, they will work with this mod.

Divine spells, on the other hand, must have the normal SPPR101-150 naming scheme to be picked up by this mod. Alternatively, if you use a sphere system with Faiths & Powers, then any spells in that sphere system will be picked up.  If you want, you can make a custom version of the sphere system that includes Olvyn's divine spells. Then, since they are part of a sphere system, they will be included in this mod.

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Thankee for seemingly making OlvynSpells and Unearthed Arcana mods compatible - finally!  Alleluia!

For purely spontaneous casters (mostly Sor), does this allow for level-by-level spell swapping from all arcane spells, such as having OlvynSpells installed?

Edited by Endarire
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43 minutes ago, Endarire said:

For purely spontaneous casters (mostly Sor), does this allow for level-by-level spell swapping from all arcane spells, such as having OlvynSpells installed?

No - this mod doesn't touch purely spontaneous casters. Those are still governed by TnB, and they don't work with the Olvyn spells. Switching spells just lets you use the normal spell-choice mechanism; so if that doesn't work with the Olvyn spells then switching will be no different.

If you want to use Olvyn's spells with these mods, play some kind of mage. Or, a single-class sorcerer without spell switching installed.

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47 minutes ago, Endarire said:

How does this mod work for divine casters who use the standard (non-sphere) spell system?

Same as any other casters. You click the 'Change Prepared Spells' ability, and that will give you access to your spell slots in the priest spellbook screen. Set some spells to be memorized, then go to sleep. A few seconds after you wake up, you will lose access to the spell slots in the spellbook screen, and you will be able to cast your prepared spells spontaneously. 

When you wake up, you may see your 'Cast Spell' button wink off and then back on again over a period of about 1-3 seconds. You will probably see that happen every time you wake up from resting. That's an indicator that the system is working.

I should probably post some screenshots/screencasts of this in action, so people know what to expect. But I don't know how to post videos. Anybody know a good method for that? (Like, how best to encode them, and where to upload them for linking?)

Edited by subtledoctor
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Guest Modtester

Hello subtledoctor,

since i really like playing with the spontaneous spell casting system of sorcerers and shamans, this mod sounds amazing. While playing around with this mod I noticed some issues:


There is a bug that affect all spellcasters at lvl 1:

When you begin the journey in cancelkeep as a generealist mage everything works as shown in your video. You select 1 lvl 1 spell in the character creation, then wait a little bit after the intro cutscene and you will see the casting button go dark and light up again. You will then have 2 castings of your chosen spell and everything seems fine. But when you use the 'prepare spell' special ability to change your memorisation slots and then rest at Whintrops Inn, the spellcasting button wont light up again after a little bit of waiting and you cant cast any spells. If you then rest again without using the spell prepare ability you will be able to cast spells again but you will now have 4 casting slots instead of 2. You can repeat this process multiple times and always get more casting slots as a result. But once you level up to level 2 or higher  this bug seems to fix itself and you will always have the right amount of spell casting slots appropriate for your level. For example: even if you got 10 level 1 spell slots at lvl 1 using this bug repeatetly, you will get 5 lvl 1 spell slots if you use the console to give yourself  161k xp and level up to lvl 9.

Atleast this bug fixes itself and wont happen as long as you dont change your prepared spells until you reach level 2.

Unless you are a specialist mage


Specialist mages: When you create a specialist mage i bg1 you will be asked to select 2 spells even though you only get 1 memorisation slot. This will usually result in the bug descriped in 1).

Furthermore it is interesting to note that you gave 1 less memorisation slot per level to specialist with the result that an invoker for example will have 1 lvl 5 casting slot character lvl 9 but no memorisation slot for lvl 5 spells. But since specialists always have spells of there chosen school prepared you can still cast anylvl 5 invokation spell. I think that gives a nice touch to specialists but this leads to 2 problems:

2.1) this behavior makes a rebalancing of spell schools a conceptual requirement for this mod, it seems you have designed specialists in this mod around your tome and blood component that does exactly this but it is not mentioned in the readme and i think it should be even though it is not technically required

2.2) Wild mages are kinda fucked. They get 1 fewer memorisation slots than generalists just like the specialists but they get no sepecialists spells prepared. Which means for example a lvl 9 wild mage cant cast any lvl 5 spells. Is that intended? I suggest that they get the same amount as generalists since they are balanced somewhat thrugh the 1in 20 chance of a wild surge every cast. But there is an even bigger Problem for Wild Mages:


There are no scrolls for Wild mage spells in the game which means they dont get converted at all into the 5e system. You can prepare Nahals Reckless Dweomer and Chaos Shield but they will never show up under the casting button.

I found an easy fix for this: I created a scroll for NRD and CS, put them into the override folder and then reinstalled the mod. Now NRD and CS are atleast castable now.


The ring of evermemory: When i use the ability to refresh my lvl 1 casting slots nothing happens. But interestingly when i unequip and reequip the ring after using its ability my spells do get refreshed. This ability is also not limited to 1x per day but can be used repeatedly unlike stated in its description. Furthermore you do get 1 extra memorisation slot and 1 extra casting slot while equipped which is also not mentioned in the item descrpition.


Whenever i cast a spell with this system i get 2 messages in the combat log for casting.


There is another engine quirk not yet mentioned in the readme: What many players dont know is that since patch 2.5 (i think) there is a hidden option in the baldurs gate options lua file that lets you show the radius of spells and abilities. This function does not work with the 5e casting system.


Caster level vs. Character level:  For single class casters this is not an issue because for those the formula is that Caster level = Character level. But for multiclass characters it doesnt seem that simple in the IE as far as i know. If you create for example a cleric/illusionist multiclass and give it enough xp to get to level to lvl 3 cleric and level 2 illusionist the arcane casting slots you get are as if you were a level 3 illusionist. That means that you can cast an illusion spell of spell lvl 2 even though you shouldnt be able to. It seems that the castings slots are determined by your overall character level and not by your level of the illusionist class. Like this example shows that can result in some inconsistencies with your casting slots regarding your mage level in case of multiclass casters.




This is mod is actually in a very well playable state if you install the components from tnb mentioned in the readme plus the component i mentioned in 2). The problems in 1) and 3) are easily fixable and I think and the other problems are not that big of a deal and maybe there are workarounds for those


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Guest Modtester

I found one more thing regarding mage multiclasses:

When you equip an armor it says that spell casting is disabled. But with this system you can still cast spells regardless. But if you have armor equip after using the prepare spell ability and keep wearing it during rest your spells wont get refreshed


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