User:Average/Luck
Luck is a hidden stat that is kept by the DM. If a player has it, it can only be "blessed", "good", "bad", or "cursed". If good, players get advantage on rolls. If bad, they get disadvantage. If their luck is blessed, they get advantage on every type of roll, otherwise, it's just for their main character trait (damage for fighters, healing for clerics, etc). How long it lasts depends on how they keep their alignment and play out their karma. Mana may drain faster or slower if "blessed" or "cursed", respectively.
Hidden secret: luck is always good when you are going with your gods and your gods are more powerful than the others domineering the realm. If you are tackling something your gods know not, it's neutral, as both the gods and the character are finding their way through the Unknown. Generally, the gods do not want to get in trouble with any other gods that might be in play, so they remove their connection offering luck. If you and your gods are successful, you gain the rewards and luck improves, if you are unsuccessful, you gain bad luck from whatever forces that conquered you. You generally can only gain it back by serving your new master to some degree.
If the luck is by a male god, the advantage is on DMG rolls, if by a goddess (or from an amulet by a Herbalists), then the advantage is on HIT rolls.
Generally advantage rolls are +HIT.