Fatigue

Fatigue or vigour is a mechanic that affects units in battle.

Units tire as they move and fight, meaning that they cannot engage in combat as effectively. The vigour/fatigue level of a unit is shown on its tooltip. Troops recover vigour slowly over time if allowed to stand still. Walk units where possible and only charge them at the last moment to prevent them from tiring.

For undead races such as Vampire Counts and Tomb Kings, the different levels of fatigue have different names. This represents the fact that undead units don't get tired, but instead the magic sustaining them can run out.