Sources of regeneration

[temnix]

In these games, does all regeneration come from creature rings? There is also the potion and the removable ring, and Constitution works to heal at higher levels, although that doesn't use the Regeneration opcode. Are there any special sources or ways of applying it? I don't really need to know the names of all items with the R opcode, I can just patch them, but I would like to know any special accents there. Is there any reason not to replace R with a cycling Current Hit Points bonus? The point is that the latter can bring creatures back from the dead, while R stops with death.