Seatroll submitted this

The entrance to the second secret level is to be found on level 15 (15 !
validated that before I wrote this ;) ). In Level 15 the player will
discover an ancient dungeon and in there get to a room full (!) of extras !
2 level advancements, 1 secret level entrance and about a dozen of "fortify
dungeon" specials. BUT ... the rooms is full of traps too, build like a
chess board, 1 field bonus, 1 field trap. Took me about 2 Level 10
Skeletons Warriors and 10 - 20 Imps to "disarm" all traps by setting them off ;) ...
But the level contains 6 gem fields, so don't worry about the costs to
summon enough imps ;)

Ah... there IS more!