The Rowan Staff was a magical staff and a powerful artifact of the Old Religion, carved from the Rowan Tree that grows at the very heart of the Isle of the Blessed. Only the High Priestesses and their Blood Guard had ever set eyes on it.
Morgause, a High Priestess of the Old Religion, gave the Staff to her half-sister Morgana in order to allow her to perform necromancy. Morgana, in the beginning, was unsure about using the Staff because she thought her magic was too weak to wield such a powerful instrument, but Morgause ensured her that the Staff would guide her, because it carried its own power.
During the Great Battle for Camelot, Morgana went to the castle's vaults, where many knights had been buried, and drove the Rowan Staff into the stone floor, screaming and releasing a blast of energy that only those with magic could feel. As she watched, the Staff's power allowed her to perform necromancy, as dozens of skeletal hands burst from the floor of the crypt. Morgana didn't have to chant a spell, because the Staff's power was strong enough and it was the Staff itself that guided her. She awoke Camelot's dead warriors in order to force Camelot's Knights to fight on two fronts, as the invading army surged into Camelot and the army of skeletons attacked from the heart of the fortress, and against an immortal army.
The Staff was later destroyed byMerlin, who had defeated Morgana with magic. The young warlock shattered the Rowan Staff in two parts using his sword and a spell ("Snæde!"). This caused another magical blast of energy to be released and the skeleton warriors to collapse into inert piles of bones as the enchantment that kept them alive had been broken (The Tears of Uther Pendragon).