Heres a tip FOR ALL THE PEOPLE SAYING YOU CAN FORCETAME IT IN THE ARENA- if u go into the bosses arena and forcetame it.... you'll be stuck there forever bc the boss gotta die in order for u to leave. :)
To kill it use a sniper and shoot the opening in the center of the diamond shape thing then that’s how you damage it. If you attack the outside it does nothing it just damages you I hope you follow that tip. Trust me.