In a world without trample, one card becomes an aggro killing machine.
Splashable in any deck
More powerful than a token blocker
Able to chump large creatures with a single tap!
Look up in the sky, its a bird, its an angel, no..it's
Will-O-The-Wisp in a Swamp!
I think if anything, you might decide to not give this thing an ability, but if you do, it shouldn't be to give any deck an easily splashable 1/1, flying, regenerator. Dryad Arbor is nice because it's similar to llanowar elves with "This is uncounterable" tacked on. This thing is INSANE though. Maybe something like B, Pay 1 life: Regenerate or even better: B: +1/+0 Sortof like an uncounterable shade. It's never going to be used to pump itself, unless its blocking...and it won't be an easily splashable aggro killer.