Nils, Discipline Enforcer (SOC-158) [Commander: Secrets of Strixhaven]

At the beginning of your end step, for each player, put a +1/+1 counter on up to one target creature that player controls.

Each creature with one or more counters on it can't attack you or planeswalkers you control unless its controller pays x, where X is the number of counters on that creature.