Teysa of the Ghost Council [Alchemy: Outlaws of Thunder Junction]

Starting intensity 0
When Teysa enters, create a 1/1 white and black Spirit creature token with flying. Teysa intensifies by 1.
Spirits you control get +X/+0, where X is Teysa's intensity.
At the beginning of your end step, you may exile Teysa. If you do, at the beginning of your next upkeep, return Teysa to the battlefield under its owner's control and it gains haste.