Bonus as a companion: +1 AP to all art or literature of the stryx it's equipped to. This bonus only applies to art/lit posted after the date the rock was equipped.
Please note: Unlike other companions, rock companions are non-transferable. They're one time use companions only. Once they're equipped they can not be transferred to any other Stryx. If they're removed, or switched out with another companion, the rock is gone forever.