Oketra the True

Oracle Text

Double strike, indestructible

Oketra the True can't attack or block unless you control at least three other creatures.

3W: Create a 1/1 white Warrior creature token with vigilance.

Card Rulings

4/18/2017 Once Oketra has attacked or blocked, it will remain in combat even if the number of other creatures you control becomes two or fewer.
4/18/2017 You don’t have to attack with three other creatures for Oketra to be able to attack. The same is true of blocking.