So {Tidebinder Mage} {Thassa, God of the Sea} and {Master of Waves} on the bf. I cast {Prime Speaker Zegana}. Wouldnt thassa become a creature before zegana checks for power? So zegana would get five counters?
That's actually a pretty tricky one. But I'm afraid it wouldn't work out. Prime Speaker enters with the counters already on her (not an ETB ability). Thassa won't become a creature until after that, once the state is next checked after Prime Speaker is on the battlefield.
If it were an ETB ability, Thassa would be a creature before the ability resolved. But I'm afraid this way, Prime Speaker is entering with counters BEFORE Thassa is a creature. Then Thassa shows up just a split second late to the party.
Oh right because the text reads "enters the battlefield..." not "when enters..."