|Out of universe information|
He warned them not to enter Merlin's library but SG-1 did not listen. When Antonius was killed by the Black Knight, he demanded they leave his village and take the curse with them. After Dr. Daniel Jackson and Lt. Colonel Cameron Mitchell reentered the library and the Knight appeared again, he believed Mitchell brought his death onto himself.
Fortunately, Valencia pulled the Sword In The Stone which allowed Mitchell to hold off the Knight long enough for Jackson to shut down the hologram. He reluctantly entered the library and Jackson inquired about the Sangraal. He told them that King Arthur and his Knights left to quest for it long ago on the planets Castiana, Sahal, and Vagonbrei. (SG1: "Camelot")