The Aetherformer

The Aetherformer enters tapped.
When The Aetherformer enters, exile the top seven
cards of your library. If no land cards are exiled this
way, sacrifice it.
{t}: Put a land card exiled with The Aetherformer
onto the battlefield tapped. Then, if there are no
land cards exiled that way, sacrifice The
Aetherformer.
(inspired by TheKeefMan)