In Respected citizen quest (Shadow of Nerekhall, page 27) "Unearthly Power" influence text says:
" If Thaakiel consumes a captive thief, he may immediately move up to his speed and then perform an attack " Can Thaakiel use basic attack and captive thief to attack second time?

I know basic rule is that monsters can attack only once when activated, but encounter rules say "Each time Thaakiel consumes captive thiefs he gains certain influence effect" So I'm confused what exact ruling is.

Based on the quest rules, it would be my interpretation that the actions are granted by the influence effect and are therefore additional (similar to the attack action granted by Frenzy.) However, I'm not aware of an official ruling on this, I'd recommend checking via the rules question link at the bottom of this page.

I don't see why Thaakiel couldn't attack, then consume a thief to move+attack, either.

Narav - just a suggestion. You're likely to get more responses if you give more context - quote rules text, say where exactly the question you're asking comes from.

I read a post like yours and my immediate thought is "I'd like to help this guy, but I'm not going to go hunting for whatever he's talking about."

Based on the quest rules, it would be my interpretation that the actions are granted by the influence effect and are therefore additional (similar to the attack action granted by Frenzy.) However, I'm not aware of an official ruling on this, I'd recommend checking via the rules question link at the bottom of this page.

I don't see why Thaakiel couldn't attack, then consume a thief to move+attack, either.

Thanks for answering. I think so too, but I wanna be sure. Because Thaakiel can attack 2 adjacent heroes, using normal attack + Unearhtly Power influence and frenzy seems to be very lethal combo.

Narav - just a suggestion. You're likely to get more responses if you give more context - quote rules text, say where exactly the question you're asking comes from.

I read a post like yours and my immediate thought is "I'd like to help this guy, but I'm not going to go hunting for whatever he's talking about."

Thanks for telling this. I really appreciate it. I edit it and tried to give more information.

Thanks for answering. I think so too, but I wanna be sure. Because Thaakiel can attack 2 adjacent heroes, using normal attack + Unearhtly Power influence and frenzy seems to be very lethal combo.

Yes, but that assumes that the heroes leave two people adjacent to Thaakiel in the first place. I would think of that as poor planning. You cou;d get around it anyway if you had a dash, but that's using to great OL cards.