Scriv, the Obligator

Legendary Creature — Inkling Bird

Flying, deathtouch
Whenever Scriv enters or attacks, create a white Aura enchantment token named Contract attached to target creature an opponent controls. The token has enchant creature and "Whenever enchanted creature attacks, it gets +2/+0 until end of turn if it's attacking one of your opponents. Otherwise, its controller loses 2 life."