Quetzalcoatl
From The Stargate Omnipedia
"Giant alien" inhabiting the thousand-meter-high pyramid on P7X-377. Members of SG-1 encountered Quetzalcoatl face-to-face after being exposed to the radiation of the crystal skull.
Quetlezcoatl was aware of Nicholas Ballard's previous journey to the pyramid after being transported by a similar crystal skull he found in Belize many years earlier. The alien agreed to form a tentative friendship with Earth, on the condition that Ballard would remain as Earth's envoy.
DETAILS
PLAYED BY - Christopher Judge (voice)
FIRST APPEARED - Crystal Skull
KEY EPISODE
Crystal Skull - Quetlezcoatl welcomes SG-1 with the Mayan words "the enemy of my enemy is my friend."