Zelos was the other final Chosen for the Church of Martel in Tethe'alla in the original game. After the Chosen system was abolished after the reuniting of the worlds, he pushed for major reformations within the Church itself.
Zelos uses his good looks, popularity, and carefree personality to obtain valuable information from the citizens of Meltokio. Although he appears to be a flirtatious woman-chaser, this is nothing more than a mask --- he is actually a calm, insightful person (the "mask" was made a joke of with a specific title in the original game).