Walkthroughs for custom maps.

Opened the map in the editor and carefully removed the magic clouds: there was no pit there initially. If someone else created the pit, then there is only one disappointing possibility: due to a bug in the game, some enemy hero flew there without having the right to do so (I have observed such flights repeatedly, and I have saves that demonstrate them).
The Grail was missing in the Necropolis of Jorune (cell 123.9) at the start. This means that someone placed it there.