The Army of the Dead comprised Nightsister Zombies located on Dathomir. These undead warriors were summoned by the Nightsisters to oppose the Confederacy of Independent Systems amidst the Separatist invasion of their planet, which also served as the homeworld of the Nightsisters.
In an effort to prevent Grievous and his troops from completely destroying the Nightsisters, Daka raised this army during the Battle of Dathomir. The Nightsisters gained an advantage until Grievous breached the secret cave, killing Daka. This resulted in the demise of the undead army and the remaining Nightsisters being overwhelmed. The Nightsisters suffered a massacre, and the village was devastated.