OK! It turned out I had completed two of the three quests in the fourth lower level of Durlag's Tower. The WT said I was ready for the Demon Knight, but the ghost of Durlag thought otherwise.
As I'd been away from the game for so long, I didn't know what I'd really done before. Apparently I'd just descended to that level, and the two quests I did yesterday were the second and third. I found the first one pretty easily, but I have to say that it was the toughest. Some enhanced phase spiders and ettercaps. Every time I thought I'd got 'em all I'd move farther into the room and more would appear. However, I smashed 'em, finally.
The problem was that I didn't get Imoen to detect the traps. The traps merely shot out webs that immobilized my party for a goodly number of turns. Must have got caught at least five times, the last one when one of the characters wandered and sprung one (this game is kind of notorious for bad tracking--some characters, especially Neera, just wander off and take the long route around if you don't catch 'em). It was merely annoying, not dangerous.
Anyway, I finally got the quest to kill the Demon Knight. Now. I've got the WT, and I'm certain it would work IF I had a cleric, which I don't. Ergo, I cannot use the "animate dead" spell to get some skeleton warriors to distract the Knight. I'm following all the other instructions, but the verdamnten Knight follows Ajantis and kills him without those distractions. I've managed to kill him a few times, but he always gets one of my party, usually Ajantis, who gets stunned and can't defend himself.
If I can keep the Knight away from him that might work. I've got one potion of invulnerability, so I'm going to give that to Ajantis and try monster summoning and running away, giving my protagonist (who will always and forever be called Emerald for my precious kitty), who is pretty strong, the option to beat on the guy. If I can get my mage away from him fast enough, the summoned monsters might distract him the way the skeletons do in the WT (there's even a nice video of the strategy.)
If I can't get him, at least it's an optional fight. I can go back to a nearby room and ask the spirit to get me outta there. I've got all the loot except whatever I'd get from the Knight.
Still, I wanna get him! I'm going to keep trying. I've killed him a couple of times. I just need to keep all my characters (barely) alive until I manage it.
Maybe tomorrow.
Still, this is fun!
Update: Aha! The summoned monsters are going to work. I have a couple of monster-summoning wands. The problem is that my mage has to approach the Knight halfway down the stairs to use the wand. It works though. I tried it, and it does summon monsters that distract the knight. Now I have to get the timing right. Ajantis has to make it as far as possible across the room (as in the video), and my mage has to summon the monsters and then get outta there. So it's all going to depend on timing, but I believe I can do it. Just not tonight!