When the battle phase starts, each player may put 1 captivity counter on a unit.
Each unit with 1 or more captivity counters on it gets Fury 1.
Once per arena per game, each player may choose a unit in that arena with 2 or more captivity counters on it. Each unit chosen this way gets "Upkeep: Pay 1 Force, discard a card from your hand, or tap this unit." until it is discarded