With FAQ 1.9, Monster of the Deep's card reads "Corrupt this unit to choose up to 2 target units. Those units cannot attack or defend until the end of the turn," It sound to me like the act of corrupting the Monster is the cost.
Actions are taken in a "first in/last out" order but costs are paid immediately. So I couldn't use the core set Chaos tactic Seduced by Darkness to prevent this action right? If I play it after he declares his action, his cost is paid first (corrupting), so my corruptiing of his monster doesn't happen because he's already corrupt. If I play it before he takes his action, he can just respond by taking that action first.
I hope I worded my question clearly enough. Am I understanding this situation correctly?