ATM there is only 1 power stone, there will be more eventually and they are based off of the ones from atlas...


The purple power stone is used for initiating the hellraiser tame by force feeding it one while its unconscious

The purple power stone can be acquired by killing the arch tempered carnotaurus or the arch tempered tyrant. Both have a chance to be summoned when you spawn in the AT summoner (look in engrams). The scourgion queen will not drop power stones but will drop reaper pheramones, allowing you to get them on other maps.

The power stones are also used to craft other boss summoners (in case those bosses arent spawning on your map)