Regret

Defender
When regret enters the battlefield, choose a number between one and six.
Regret gets +1/+1 for each card exile with it.
If Regret’s power is six or greater, it can attack as though it didn’t have defender.
At the beginning of your upkeep, reveal the bottom four cards of your library. You may exile any number of cards revealed this way with the chosen number indicated in their mana cost. Shuffle the others into your library.