This can be entered from the Rune Room and has exits along the outer corridor to the Mausoleum and, past a guard who we were told about earlier, to Level 4 and the King's Domicile - my favourite area ... you will find out why later. You need the King's Pass to get past him and you will find that in the centre area. This can be reached by teleport from the Basement and has a teleport in it to another part of the King's Domicile. Otherwise you can enter from a door along the north wall but you will need to trek round to it. Several tapestries give info as do runes by doors. Basically you need the King's Ring, Lockpick, and Key to be able to travel around freely. Later the Domicile Key will open the door at O8 but we haven't got that yet (well, I didn't!) In the centre area is the Wizards' Challenge. Unlocking doors and fighting, make your way around. Certain tapestries will only be legible if you are of a certain class or race. Fight at E8 for the King's Pass. Note, you'll need several to complete the game as Deldwin wants one each time you pass him, but you can't win another one until you have used the first. There are a few one-way doors too, just to make life complicated.
I played as a human knight pledged to Harmony (Mr. Nice Guy) so this is what happened to me. At I7 I was told I had mastered the Challenge and was told to enter the door of Harmony. (Similar blurb awaits those of Chaos at H7). The door is at I8 (and for Chaos at H8). Inside I8 are two rooms, each with a big fight. I used Control and Poison Cloud with healing when necessary. The second fight, at I10, is the bigger of the two. Of course, you have to go back through the first fight again on your way out. Head to J7 and a door will open in the north wall. Inside in K7 is a MAJOR fight with wyverns and demons. Good luck, you'll need it. But when you win, you'll get a Chess Piece inscribed 'Property of Arnakkian Slowfoot'. Useful or what ...? Being a coward, I didn't try the other door marked for Chaos!