I’ve heard rumors that it’s possible to activate Mayhem Mode on the second playthrough as soon as Sanctuary III is available in the story. I’m now Lvl 12 Gunner on Promethea and still the Mayhem activation pedestal is not spawning, but the Guardian Rank page in the menu is unlocked. Playing on the Xbox btw
Wait at level 12 ?
You unlock the pedestal after beating the game and you can then use it on normal and tvhm (pc) but only with the characters you beat it with.
Since you are on console: There is currently a bug that does not enable the pedestal in TVHM from the beginning. You have to finish the TVHM first and then you can activate it.
I still believe the real bug is that it’s available on PC right away. “Who volunteers for taking that away from the PC gaming community?” “erm… no, I’m good, thanks”