Good morning to you all!

Was playing yesterday and something came up;

Monster in the deep was in play "Action: Corrupt this unit and choose up to two target units. Those units cannot attack or defend until the end of the turn."

When can this ability be triggered during the battlefield phase?

Exemple:

I declare my attack phase. I then proceed to declare which unit will attack, and select 3 units.

-Does it need to be triggered before I declare my attacker, as once they are declared, they are already attacking (kinda like Corruption work).

or

-Can he trigger the ability after I declared my attacker, meaning he could "stop" 2 of my 3 attackers from attacking, leaving my single unit sacrificing himself into a somewhat glorious death without me cancel the attack?

If I'm not mistaken in the rule book, actions cannot be taken while I declare my attacker, so can this ability remove a already declared attacker from combat?

Thanks for your time

Note; this game gets a bit complicated... but ****, it make it so much fun!

Monster of the Deep has an errata, it should read "Action: Corrupt this unit to ..."

You're understanding it correctly though. The Action can be used during any action window. There are several of those during the battlefield phase. If you corrupt a unit after it has been declared as attacker or defender, it will still attack or defend normally. If it is corrupted before, it cannot be declared in the first place. During the battlefield phase, you first declare the target of an attack (the zone, legend, or fulcrum in multiplayer), then there's an action window before attackers are declared. That would be the last opportunity to use Monster of the Deep's Action to corrupt units and keep them from being declared as attackers. But of course it could be used earlier in the turn too.

Totally make sens than!

Thanks!