The Cerberax is a 3 (technically 4) part tame. When you knock it out, one of the three heads will pop up and be able to be ridden. You will have to repeat this process 2 more times before tranqing it a final time to allow the normal feeding process. When successfully completing a task the Cerberax should launch you off its head and roar, giving you time to flee.

The lightning head will have you play a minigame where you must keep a slider over an arrow and keep doing so to fill a bar.

The fire head marks a target for you to kill, each kill giving a % of your bar (not sure what affects this).

The poison head will require you to feed it, seemingly accepting the food from your last hotbar slot. You can only feed when the head begins to turn and snap at you.

Once you’ve completed each head, the final knockout will be a regular feed. Good luck!