After speaking to the Dead Girl, you can proceed to Valak's Mausoleum. Once inside, start buffing (by yourself or with the help of a caster) for that much needed protection – stone skin, fire, acid, and sonic (for the traps), jump, bless, good Knight Online Gold hope, and other buffs to help increase your AC.
It'll be a great idea to bring a Rogue to disable Valak's nasty traps. Finally, make sure that you’re Sorcerer, Bard or Wizard cast haste.
They can take turns casting hastes so no one caster would have a more depleted spell point level than the other. Haste is a must in this quest because of the time limit requirement.
After the first of the many haste spells is cast, run until you find the first set of switches - one on the east and the other on the west. Once you pull the switch, you'll be attacked by several skeletons. They hit hard, so make sure the Cleric is keeping tabs of your health bars.
The Bard can also take the role of a back up healer, because as the group progresses, it'll be tough for the cleric to heal everyone.
After subduing the pesky skellies, you can move to the second set of switches just a few steps north. The path has exactly the same design, so you wouldn't miss the switches.