What Frost ideally envisioned was to create an offshoot of his current dungeon, not necessarily creating a second dungeon but another entrance that differed from the current layout. He first wanted to attempt such a notion and see if the dungeon menu rejected his proposal as it has happened before putting all his eggs in one basket.
Frost along with a great number of his siblings attempted to push the boundaries of their dungeon creation skills over the past few months with a great many being shot down by their father's 'actually' fairly rule bound system.