If you die on the same frame as falling down a hole and the screen transitions, it increments the submode which results in a broken mode-submode combination. The room number in RAM changes to that of the room below, however it is never loaded. Thus, transitioning north places you in the room north of the room below this one, from which you can jump through a wall to activate EG. This also underflows the room number from 10 to 250 which causes all sprites to despawn, including the mantle blocking the sewers in Escape.

The Book of Superskuj, 753:12-15