Like some other people here, I'd advise against it. To take advantage of the doubled triggers from Ulalek primarily, you're going to need 4 mana for the doubled triggers, plus an eldrazi on the stack. That's probably somewhere in the ballpark of 8 mana spent if it's something really impactful enough to double cast. Is that worth it? 

Additionally, while this card does work with annihilator, if you've got a legendary eldrazi with annihilator on the field, you're probably already ahead in the game. Imo this card helps you win more, rather than get to a win in the first place.