Level 1-10 are quite easy, I suggest DPS characters to use a vit pet summoned so you can heal yourself
If you are a hrtc you are going to need a DPS pet since you can heal yourself.
Now the level10 boss is pretty easy, My suggestion for getting through the stairs is killing 1 by 1 if you are not a high powered character.
lvl 11-20 are fairly easy. What you want to do for the level 20 boss is save up alll your high powered hits and hit him with it asap when hes about half hp.
Here is when it starts getting tricky. On each floor there are 8 mini bosses and 4 sets of 20 mobs per floor, the mini bosses have certain skills they use. if you get the one that summons the portal you HAVE to kill the portal first because it will non stop spawn mobs and eventually over run u and kill you.
Once you make it level 30. The boss is 3 angels. If you are a high power dps class you can take on all 3. But the best way to do this boss is to save up your exalt so u have extra XP's against the boss.
The boss spawns 3 angels and the angels revive each other. You have to kill all 3 and a statue will spawn. But if you do not kill the statue fast enough it will disappear spawning all 3 angels in a rage and u will die.
My suggestion...Save all ur hits for statue if you're a hrtc. I always recommend transforming against this boss since they hit hard.