dtgreene: Personally, I was surprised that the healing bug appeared in the second game, especially since the first game didn't have it, despite having the abilities needed to trigger it. It seems someone must have messed with that section of the code and introduced the bug.
For reference, here is how it could be exploited:
Your party should have the following:
1 Half-Giant Fighter (Gladiator also works here). Get CON and HP as high as possible at character creation, and choose Psychometabolism as the discipline (for Lend Health). Note that this character has to be created in the second game; wild talents don't get Lend Health in the first game.
1 Druid (any Sphere) or Cleric of Water. At level 11, this gets you Heal (Druid) or Water of Life (Cleric, works exactly like Heal contrary to what the description would suggest. This character will need to be at least level 11. More characters of this sort will let you get even more HP.
1 character to receive the HP. This can be the priest, but it has to not be the same half-giant. For most dramatic results, I will assume this character is a Preserver with low HP, but that isn't required.
The way it works is as follows:
1. Cast Aid on the preserver. This will raise her HP above their normal maximum. (The bug only triggers when HP is above its normal maximum.)
2. Have the Half-Giant use Lend Health on the preserver. This will transfer all but 5 of the Half-Giant's HP, giving the preserver an enormous amount of HP.
3. Cast Heal or Water of Life on the Half-Giant.
4. Go back to step 2.
Repeat until out of Heal/Water of Life casts. Your Preserver should now have several hundered "temporary" HP, which last until lost, replaced (so don't cast Vampiric Touch), or your party rests (but then you can just do the trick again).
There's also weird little things you can do with the Reincarnate spell.
By the way, Wake of the Ravager actually has 8th and 9th level spells (accessible by cheating), but they are in various states of being functional. For example:
Meteor Swarm: Works well. You get to target each of the 4 meteors separately, meaning that this would actually be a rather nice spell if it were obtainable.
Time Stop: Prevents your turn from ever ending (though note that movement is never restored). This can either trivialize the battle or (if you run out of ranged attacks) softlock the game.
Prismatic Sphere: Crashes the game.