On the world where the Sangreal had been hidden, Morgan Le Fay had put in place several safeguards to ensure that the key to Merlin's weapon could only be claimed by the most virtuous and true of spirit. The forest had been enchanted with tests to prove one's worthiness, and the Sangreal itself was said to be protected by the most powerful of magical beasts, a dragon. SG-1 had not taken the legend literally, but after conquering each of Morgan's challenges they reached the cave beneath the lone mountain where a hologram of the Sangreal rests, and as Daniel attempted to grasp it, a huge dragon appeared from the depths of the cavern.
The dragon was enormous, with a wingspan easily reaching 40 to 50 feet. It breathed fire and was capable of flight, chasing the team from the cave to the forest. It was not a hologram and did not appear to use a force field for protection, but its body armor was so strong that P-90 weapons fire bounced off without penetrating. SG-1 attempted to use C4 against it, however the dragon swallowed the explosive tossed toward it and suffered no injury when the C4 exploded.
The Parchment of Virtues had stated that "the Sangreal shall belong to he who speaks the guardian's name." To know something's secret name is to steal its power, and name magic is common in most mythologies, however SG-1's suggestions for the dragon's name failed with guesses including Darrell, Smokey, and Puff. It was not the dragon who was the guardian, however. The guardian was Morgan Le Fay, who had devised the safeguards to protect the Sangreal. When Daniel called out "Ganos Lal," Morgan's name in Ancient, the dragon instantly vanished in a brilliant flash of light.
Episode Reference: The Quest