Prevent monster heal, can merc apply

[adeyke]

You don't have to deal damage to the monster in order to apply OW to it. However, if the monster is at full health, it doesn't regenerate at all, so the negative regeneration from OW is ignored. That means the OW will remain in a dormant state either the 8 second OW timer runs out (in which case the OW disappears) or the monster drops from full hitpoints (in which case the OW starts taking effect).

This means that a pure physical character can apply OW to a PI monster, provided that someone else manages to damage the monster (any amount will do).