Cubic Gate ideias

My players just defeated a Adult Black Dragon at lvl 9, they get a lot of healing potion before, acid reistance potion and a lot of stuff. When they defeated and find the treasure hoard they rolled the magic itens as described in the Fizban and with a incredible luck they get a cubic gate.

I don't know how I going to balence around this. I want cool ideias to balance and places that are already in the cubic gate.