On the right side of Becks there is a big bell that you can interact with. If you use it, that person will be transported to a room with a couple of normal monsters, kill those and Becks will take triple damage. (need verification on this) It is not necessary to use this though.
After defeating Becks, the doors open and you can move up the staircase. And Becks has 253,045 HP
Pooch & Tack
The second boss are guardian dogs named Pooch and Tack.
They can be pulled seperatly increasing your chance of survival. Though they are not incredible powerfull they can still pack a punch without heals or buffs. If you do pull both at the same time, split up your party and fight them. A good solution is to have a warrior solo one, using tcos gold Disarm as much as possible to reduce damage taken.
Pooch uses normal melee hits, nothing really worth mentioning but they can hurt. Tack does the same except he can teleport you away from him. It does no damage but it disorients you. Tack seems to have less resistance then Pooch, and dies faster. So far, it seems that Pooch has a higher chance of dropping the APP necklace (best drop in this instance). However it has been said that any mob in the instance can drop it.
After disposing the guardian dogs, move up the staircase again and into the final room. Before entering its a good idea to discuss the tactics for Amsell.
Both dogs have 54,293 HP
Amsell
Amsell is in a big room, really nice looking place. Around him in the corners of the room are four crystals. As soon as Amsell starts his conversation, his minions will spawn. Destroy the crystals and the summoning will stop. Now kill the minions as fast as possible and tcos gold make sure that you stay out of range of Amsell. Do not destroy the crystals if he has not started his conversation/summoning. This will cause him to keep summoning to no end and you will be overrun with angry little fat ugly minions!
After there are no minions left, kite Amsell around the room. Make sure that he does not walk into any obstacles because that might cause him to fall through the floor.
Keep kiting him and keep using ranged attacks. He's not that bad in the end. His special move is a lifetap that damages for around 1,5 - 2k dmg and heals him for 10k hp! Also he has a Damage over Time spell that is quite powerfull. Keep an eye out for that.