13 levels in one hit

[the Invisible Stalker]

I decided to try, and 6 levels. It was because i leveled up accidentaly. I used deep descent.

[Philip]

level one to level ten from a skeleton human. I used a hobbit warrior.
EDIT: I got level one to level 14 right now. Black dragon fly.

[Timo Pietilä]

level one to level ten from a skeleton human. I used a hobbit warrior.
EDIT: I got level one to level 14 right now. Black dragon fly.

Dlvl 18 monster?? At clvl 1? Wow! That's impressive. That's also 75 points of XP. Only shallower monster killable with clvl 1 char with higher XP is Bullroarer, however Bullroarer moves fast and has quite a lot more HP, so killing him would prove troublesome. OTOH it doesn't have any distance-attacks so with good missile-weapon (or wand), phase-door scrolls and some luck it should be possible to kill him. With 2d6 + Fire brand oil flasks you would need approx ... three hits? Hm. That's big damage for so cheap object. Par with +8 sling and normal ammo. I need to reconsider my early strategies.

[PowerDiver]

Bullroarer moves fast and has quite a lot more HP, so killing him would prove troublesome.

Oil is light enough to throw far, and now does too much damage with the change of fire branding with the same dice. A lucky char who gets Bullroarer to approach across a large lit room should be able to kill him fairly easily even at CL 1.