Unswerving Sloth (Aetherdrift)

Creature — Sloth Mount - Whenever this creature attacks while saddled, it gains indestructible until end of turn. Untap all creatures you control.
Saddle 4 (Tap any number of other creatures you control with total power 4 or more: This Mount becomes saddled until end of turn. Saddle only as a sorcery.)