Roanne, Spirit of Forever

Spiritwalk — Whenever a spirit enters the battlefield, you may have all creatures you control become a 5/5 blue spirit elemental creature with flying. At the beginning of your end step, sacrifice all creatures you control.

Flying, vigilance, indestructible

When Roanne, Spirit of Forever enters the battlefield or attacks, tap target creature an opponent controls and put three stun counters on it.