Hex, Kellan's Companion (YWOE-014) [Alchemy: Wilds of Eldraine]

Haste
Whenever you cast an Adventure spell, if Hex, Kellan's Companion is on the battlefield or in exile, it perpetually gets +1/+1. Then if it's on the battlefield, exile it with a fetch counter on it.
Whenever you cast a spell from exile, if Hex is in exile with a fetch counter on it, put it onto the battlefield.