Edit: Scratch everything I just said.
This+basilisk blood could be a lot of fun.
It feels underpowered against your opponent (gravity pull would just outright kill the creature for half the price, this can only reduce it's attack or defense) and somewhat overpowered against yourself. This card could be severely abused by players with 2+ auburn nymphs. 5 casts of baslisk blood on any creature + this card = 100 damage.
Then again, air nymphs give you instant 20 damage without having to wait 6 turns or using another card, so it looks fairly balanced.
I like it.