Actually no, decaying touch only affect healing spells or potions, no all healing.
I am not 100% sure but really think Healing from higher than 100% resist in an element still heals you with decaying touch.
It actually works. You can create a character with the zombie talent and then cast Decaying Touch on yourself. Then poison will damage you. I used a Decaying Touch scroll on a slug to test it, and they damaged themselves on my Retaliation.
Decaying Touch just doesn't help Undead with actual healing spells.
I might be wrong, but from what I experienced, environmental effects does not trigger retribution.
Yeah. Environmental Damage doesn't cause any kind of Retaliation, just the initial damage if it was caused by some kind of attack. I can walk through fields of fire and my Retaliation doesn't trigger.
There is one definite moment where Retribution interfered with a quest, though. When Gawin teleports you, Retribution triggers and starts a fight with him.
