Whenever Navri, Hummingbird Champion attacks, target player draws a card, then target player discards a card. Then you may remove one slumber counter from target creature. If you dont, goad target creature.

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