Warlord

From ErfWiki

Warlord is a unit that has Leadership ability^[1][2]. That special (or natural) ability allows Warlords to lead other units in combat and grant a bonus to units under their command.

Apparently, Chief Warlord is not a separate class, but rather a subclass of Warlord. Overlord seems to be a separate class of units (Overlords grant units in their stack a bonus^[3], but it is not clear whether that bonus comes from Leadership ability or as a result of some special rule).

Commanders

On some occasions terms Warlord and Commander are used interchangeably.^[4]

However, Commander seems to be a more general term since Casters are Commanders too^[5], but they do not have Leadership ability.

Origin

Apparently, warlords can be trained in cities. Infantry units can be promoted to warlord in the capital (although at a high cost).^[6]