The Gods Favor skill is a starting skill of the Mercenary free to play class.
This skill is a faction skill that is gauge of your devotion to the gods, as you make Gladiator kills you stand a chance of gaining a point of Gods Favor skill. You may also get Gods Favor from completing some quests but this is not guaranteed.
Speak to the Altar at 51, 50 in the Heavenly Arena realm to get Faction rewards and Faction quests.
Combat
In combat the Gods Favor skill determines how many entertainment points your Gladiator starts with using the following formula:
Entertainment Points = (Gods Favor / 20) + 3
This means the higher your Gods Favor skill the more EP you start with and the more powerful attacks you can use at the start of a fight because of this.