Stay away, itll be a bulk rare in a month if you want one for EDH purposes
The only exception would be if the creature created a constellation trigger that targeted itself
That's quite the combination of cards, even if you're talking about 9 mana and then some for the whole package without affecting the board in the meantime
The issue is more that I'm not 100% sure where to put this, as I feel like it's ideal in a situation where you have creatures with big ETB triggers (or death triggers if you're trying to sacrifice the tokens so you can make new ones next turn), since this is pretty much asking to eat removal after you connect with a player
It may be exciting if you draw a rare card like Sephiroth, Fabled SOLDIER, but if it's your only good card that uses black mana, you may not want to build a deck around it
Once you begin to cast a spell with emerge, no player may take actions until you're done