Treasure of Crespo is famous. (ungeon is classified as A, B, and C. they can be done which same strategy but the monsters you face get stronger in order of C, B, and A.)
Just go pull the levers (cabal online alz) then the monsters will be popped out and the steel gate is opened. Steel gates are only opened by the levers, but the wooden gates are destroyable. As you go along the long path, you will find a corpse. Click it then the steel gate will be opened.
Destroy a coffin in the room then it will summons 40 zombies. There are total 4 of chests that give decent amount of DIL. There are 2 identical rooms that have a chest and a coffin. As you know, the chest will give DIL and the coffin will produce 40 zombies each. You need to kill total 80 zombies in order to break the steel gates ahead. The last part of the NO1 is to pull the lever at the very end of the path.
Once you have entered the 2 section, zombies will WELCOME you. Kill all the kind zombies and destroy the 3 coffins in order of Algol, Alderamin, and Sorcerer in order to minimize the dmg intake from the sorcerer which does magic dmg. But it's not really important of killing in order.