Xibalba feared that Manolo would succeed in marrying Maria, which will make him lose the bet he made with his wife La Muerte. So he brought to life his two-headed snake staff and tells it to make sure he wins the bet. The two-headed snakes then bit María once, putting her in a trance.
Manolo then, in his deeply heartbroken and grief-stricken belief that Maria had died from the bite, became very easily manipulated into accepting Xibalba's deal to be with her in the afterlife. This resulted in Manolo being bitten twice (once by each head), killing him and transported him into the Land of the Remembered. Later in the film, when Manolo, Luis and Carmen reach the Land of the Forgotten, Manolo explains to La Muerte that Xibalba cheated with Más y Menos. La Muerte yelled Xibalba's name and he appeared. La Muerte grabbed the snake and turned it back into a staff.