Complex sentence: In Aztec mythology, Paynal was the impersonator and messenger of Huitzilopochtli, who took on his master's attributes at official functions while his master was trapped in the underworld or otherwise unavailable.
Split into simpler sentences: In Aztec mythology, Paynal was the impersonator and messenger of Huitzilopochtli. Paynal took on his master's attributes at official functions while Huitzilopochtli was trapped in the underworld or otherwise unavailable.