Hmm... doesn't seeing that "monster" icon make you...
wanna fight?
I actually haven't yet been able to properly "complete" this subdungeon, since I haven't encountered it while holding on to the glyph. It's been changed from its earlier incarnation, where the enemy in question spawned outside of the fog, was a lvl10 that blinked and spawned a bunch of snakes that also blinked, and dropped lemmisi when you beat him, to take advantage of the fog. He was fairly tough, but very much worth the bonus EXP most of the time...
No idea if fighting him is the same since the change put him in the middle of the subdungeon.