I've ascended in nethack once (as a Monk), and gotten to The Plane of Fire once as a Barbarian. That was a sad death. I'd been trying to not spoil myself too much until I'd at least gotten to whatever area and died there, so I didn't know the peril of using conflict there. I was using my quest artifact for levitation, and I missed the message about the levitation wearing off while jamming through the instances of "The fire elemental hits the fire elemental! The fire elemental is unaffected" a hundred times a tick. I walked into lava, but I had intrinsic fire resistance, so I only got stuck. I zapped a wand of cold down to solidify the lava, and tried to use it to solidify the lava all around, but I ran out of charges. (I should have Applied it instead, to hit the squares around me.) Then I dug down with a pickaxe to free myself, but the lava came back rushing in. I end up drowning. In lava.