Unfortunately the random dungeon generation for the battlefields can occasionally result in an entrance being sealed off, or separate from the rest of the level. In the BF I think the only way to get through a wall would be to hex teleport.
Teleporting anywhere (via hex editor)There is a way to get a summoning doll though walls (
armory trick in act 1), but even if the entrance was in range, with the latest game version IIRC summoning dolls can not use stairs / ladders / etc.
