Hector was charged to guard the Fountain of Youth by Juan Ponce de León 400 years ago, he was kept alive and young by its mystical water. Unfortunately, Hex was able to force him to reveal its location. He had led a lonely existence because if he became attached to anyone they would eventually grow old and die while he would continue to live, and warned a then-10 year-old Max Tennyson (rejuvenated by the Fountain of Youth) not to long for his kind of life. When the fountain was destroyed by Ben as Heatblast, Hector revealed that the effects of its water would gradually reverse themselves after a while. Thus, he would continue to age until his death. (Don't Drink the Water)
Considering he was charged by Juan Ponce de Leon to guard the Fountain of Youth, he must have been a well trusted soldier as shown by the picture of him from 400 years ago.
His role is sort of similar to the Knight in Indiana Jones and the Last Crusade as he guards an eternal-life-giving object and stays alive by consuming the object (in the Knight's case from the object).