Xiuhtecuhtli was the Mexican god of fire and the passage of time. Every 52 years, the Mexica undertook the New Fire Ceremony, wherein a person was redefined as an aspect of Xiuhtecuhtli and sacrificed to renew time.
During the War in Heaven, Goralschai manipulated reality through the caldera so that when he was at the centre of the 1506 New Fire Ceremony he became a literal embodiment of Xiuhtecuhtli. He planned to use his godly powers to destroy existence, but the sacrificial nature of Xiuhtecuhtli's essence meant that all Gorlaschai could do was kill himself to complete the ceremony. (PROSE: Against Nature)