From Pathfinder War of Immortals, which isn't enabled.

Unified Stance

FEAT 16

Activity 1 action

Requirements You and your united companion are within 15 feet of each other.

You and your companion enter a unified fighting style that allows you to fight in tandem more succinctly. When you enter this stance, your united companion gains the Quickened condition and, when Commanded, can use the extra action to Stride or Strike.

Pathfinder War of ImmortalsORC