What Effy said. It's Geist.
Also...
Departing Elf - Could be too powerful. You can Link a lot of creatures, and the funniest thing is that the enemoy can't even kill it to ruin your plan.
Bumuse: ...and what exactly is so powerful that you make the challenge and 10 cost? The enemy also gets a pile of mutants, not just you. Still, when he can't deal 30 damage in 3 turns, then he won't get a fieldful, so... alright, I guess.
Geist: A cheap nice durable attacker. Is alright. Maybe make it gain +1 ATK for each ability use it does, for more fun.