There are two reasons a character might choose to take a patron.
The character could of course choose a patron because the character shares the patron’s goals and objectives, and wants to help achieve them.
More likely, though, they’re into it for the power that comes from taking a patron: favors.
As a character gains favor with a patron, they increasingly gain the following.
- Stigmata, observable elements specific to the patron that can reveal the relationship and be inconvenient to the vassal;
- Obligations, things the vassal is expected to do, or to not do, to maintain favor;
- Favors, special abilities and other benefits the vassal can use.
There are several kinds of favors.
Skill favors typically give advantage on certain skill checks, or expanded use of the skill. For instance, the Spirit of the Sea favor of Barakhareesh gives advantage on Sailing checks. Failing checks in this circumstance can have consequences, specific Dark and Dangerous Magic outcomes.
Skill favors rarely cost favor, but might if the favor grants an unusual use of the skill rather than just advantage when using the skill.
Spell favors can give the vassal spell-like abilities, often modified applications of spells. The Scion of the Sea favor of Barakhareesh allows his higher vassals to breathe water, as the spell one with the deep, and even to share it with others in the same use… at the cost of the ability to breathe air for the duration.
Spell favors usually require the vassal to spend a point of favor, may require Dark and Dangerous magic checks in some situations.
Conditional favors grant abilities under certain circumstances. These often involve direct side effects. The Legs of the Sea favor of Barakhareesh gives a much improved ability to swim, at the cost of land mobility, and works only with bare legs (no armor or pants, though an exception might be made for skirts or kilts). The Eyes of the Cave favor of Chalekan gives the ability to see normally in full darkness, but light greater than a lantern is painful and interferes with vision, and daylight is blinding.
Conditional favors might or might not require the vassal to spend favor. Often there are other limitations on the ability that are sufficient.