The Betrayer

Whenever The Betrayer enters, for each 2 life paid to cast it put a -1/-1 counter on target creature an opponent controls.

Scorpions you control have persist and wither.

Whenever a creature you control with a -1/-1 counter on it dies, put a +1/+1 counter on The Betrayer then it fights target creature an opponent controls.

Whenever a creature an opponent controls with a -1/-1 counter on it dies, draw a card.