Here is the
world.x0 file (312 KB) from a save in the arena, after killing the spiders. The world.* files keep track of quest opened doors as well as items directly on the ground.
1) Load one of your saves before jumping into the pit.
2) There is a book in the western spider cell you should pick up, as well as the barrel of coal from Fergus' room. Make sure you pick up any loot on the ground you wish to keep.
3) save the game under a new name
4) unzip the world.x0 file from my save into your new save folder (a sub folder in the '
..\Beyond Divinity\savegames' folder), overwriting the file there
5) reload your new save, then jump down the pit
6) you should now have walls, etc and be able to proceed normally