Void Extrapolator

Creature — Aetherborn Warlock

This creature enters prepared. (While it's prepared, you may cast a copy of its spell. Doing so unprepares it.)
Threshold — This creature gets +1/+1 as long as there are seven or more cards in your graveyard.
2/2

Sorcery

Mill three cards. (Put the top three cards of your library into your graveyard.)