Whenever Navri, the Recruit enters the battlefield, target player creates a 12/12 blue Serpent creature token with flying. Tap it and put seven Slumber counters on it. It has "This creature does not untap if there is one or more slumber counters on it." and "This creature has indestructable while it has at least one slumber counter on it."

Whenever Navri, the Recruit attacks, you may remove a slumber counter from target creature.

Next Step - At the start of your upkeep, if a player controls a creature with four or less but not zero slumber counters on it, remove Navri, the Recruit from the game. Navri, Hummingbird Champion is your nex commander.