The following is a bunch of nonsense about Nethack, which I believe will be of interest to none of my readers, so I’m putting it below the fold.
Tiresome way of defeating the Master of Thieves: Find him or let him teleport to you. Have him escape up the stairs to heal. Chase him all over the Quest Branch until you finally knock him down. (Based on my experience with Thoth Amon.)
Quick but unsporting way of defeating the Master of Thieves: Sneak into his office with stealth. Before he can pick up the magic-resistance-granting Platinum Yendorian Express Card, hit him with one of the wands of death you found on upper levels. (In related news, have reflection or magic resistance before you do the Tourist Quest.) But this seems boring, and why waste a wand charge on him when you can beat him in melee?
Moderately clever way of defeating the Master of Thieves: Sneak into his office with stealth. Have teleportitis and teleport control too. Wake him up with a dart, like one of those poisoned ones that got corroded when you mixed up a moat and a fountain. Teleport back to the stairs before he can. Beat on him with Mjollnir until he says uncle.
Actual implementation of plan:
“You throw 2 poisoned darts.
“The first poisoned dart hits the Master of Thieves!
“The poison was deadly…”
So, basically, if I don’t win now I suck (or I got mixed up and dropped myself into water with no way of getting out).