Grebe, the Unhallowed

Flying, trample, undying
At the start of your upkeep, mill X, where X is
the number of Groomsman you control.
Groomsman on the battlefield have Undying.
When another Groomsman with Undying dies,
return it to the battlefield under your control.
Wedding Party (At the start of your turn, if you
control all other Legendary Groomsman, you win
the game.)