Ultimate Ultron

Flying, indestructible, first strike
Metalcraft —Ultimate Ultron has vigilance
as long as you control three or more artifacts.
{c}, {t}: Create a 1/1 colorless Ultron Sentry
artifact creature token with flying.
When Ultimate Ultron dies, you may pay {p/c} and sacrifice an Ultron Sentry artifact creature token.
If you do, return Ultron, Prototype from your graveyard to your hand.