It makes a creature suck attack and HP from its allies to grow stronger itself.
Not sure how to make it more clear though
attack can go negative?
also, I don't really see this being used on your own creatures,
unless as a back-up plan on a momentum'd creature.
Scorpions and vampires would gain nicely from it.
Could give a quinted creature a way to heal and gain attack, turn sparks into repeatable attack power buffs, beef up high attack but low hp creatures.
Hmm... didn't think about that one.
I think this is one time when letting it drain attack to negative would be very interesting, since it ends up balancing out.
Alternatively, it could always drain toward zero so that it would drain negative attack creatures and actually reduce its own attack.
What do you think?