Souvenir Snatcher

Text:

Mutate (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Flying
Whenever this creature mutates, gain control of target noncreature artifact.

Rulings:

• 4/17/2020 Once Souvenir Snatcher has snatched a noncreature artifact, you’ll continue to control that artifact if it becomes an artifact creature.
• 4/17/2020 The control-change effect of Souvenir Snatcher lasts indefinitely. It doesn’t wear off during the cleanup step, and it doesn’t expire if Souvenir Snatcher leaves the battlefield. In a multiplayer game, it does expire if you leave the game. If the artifact’s owner leaves the game, that artifact leaves with them.