There is a way to passively tame one,but requires a trap, and one you either fail or pass blue head. You can get stuck on top of the Cerberax,stuck in between the trap top and itself. And passively tame it with kibble while on top. If you are in the right spot,it can't attack you and you can just feed it kibble every time it gets hungry. Idk if it was intended to it to be able to do so or not,but I found it out on accident. The trap consists of 8 small metal gates, 6 windowed walls,2 tek hangar doors,and a few metal horizontal pillars.