You probably want to start a fight with the Asmodians.
But your goal seems too great to me, judging by your skills. You surely don't really want to wage a fortress battle at your level.
Ugh, calm down. I'm going to help you.
You absolutely have to occupy a fortress in the Abyss.
Steal the fortress from Asmodians and the Balaur. The Abyss Supreme Commander will probably appear immediately.
Additionally, the legions that have captured the fortress are not paid by Sanctum.
That's why the legions get paid in advance and then occupy the fortresses.