Black Knight
From The Stargate Omnipedia
Guardian of Merlin's library, where his research on an anti-Ori weapon was kept.
Instead of battling those who trespass within the library, the Black Knight emerges to the villagers to incite terror and discourage re-admittance. He is governed by an Ancient control pedestal. Once the correct combination has been entered on the pedestal the control crystals can be accessible, which can terminate the knight.
KEY EPISODE
Camelot - After the Black Knight has already killed one villager, Mitchell fights it to keep it occupied while Dr. Jackson attempts to deactivate the program.