Larian Studios Forums Divinity: Original Sin 2 Divinity - Original Sin 2 - Bugs & Technical Problems Venom Coating, Decaying Touch, and Undead bug

If a character with the Venom Coating status attacks an Undead character afflicted by Decaying Touch, the additional poison damage applied still heals the Undead target, when it should be dealing physical damage, per the rules of Decaying Touch healing reversal.

That's always been how Decaying works. It reverses the healing effect from all spells and consumables on living characters. The description itself says "healing spells and potions". It does not affect how Poison works because Poison is not a "healing" effect by default. Undead, by default, are always already under the effect of decaying, basically. The only healing effects that bypass Decaying are lifesteal and Necromancy healing.