Horse Leech

Painborn (Each 1 life you pay while casting this spell pays for {1}. This creature enters the battlefield with a -1/-1 counter on it for each 1 life
paid this way.)
Horse Leech has menace as long as it has haste.
Dash {3}{b} (You may cast this spell for its dash cost.
If you do, it gains haste, and it's returned from the battlefield to its owner's hand at the beginning of the next end step.)