This feat belongs to an archetype.

A stance is a general combat strategy that you enter by using an action with the stance trait, and that you remain in for some time. A stance lasts until you get knocked out, until its requirements (if any) are violated, until the encounter ends, or until you enter a new stance, whichever comes first. After you use an action with the stance trait, you can’t use another one for 1 round. You can enter or be in a stance only in encounter mode.

Something of uncommon rarity requires special training or comes from a particular culture or part of the world. Some character choices give access to uncommon options, and the GM can choose to allow access for anyone. Less is known about uncommon creatures than common creatures. They typically can't be summoned. The DC of Recall Knowledge checks related to these creature is increased by 2.