Hecate,The Redeemed Rider

+2: Put a +1/+1 counter on target horse, Unicorn, Or Dualicorn. If a creature activates a mount ability this turn, put two more +1/+1 counters on it.
0: Until the next end step , Hecate becomes a 3/4 legendary human mounter with indestructible, haste, and vigilance
-6: Hecate deals x damage to x amount of creatures were x is the amount of Horses, Unicorn's, Dualicorn's, and mounters you control