Open the four wall safes ( -69, -128, -123 ) /waypoint -69, -128, -123 and pick up the "blue bar" to agro Nurgal.
Nurgal summons zombie adds periodically (one for each corpse in the room). If the adds get too close to you, they inflict a cureable noxious detrimental that reduces your run speed. After being up for a while, the zombies will blow up, dealing roughly 15K damage. The zombies can detonate each other and cause a chain reaction that throws you all over the area.
When he runs out of corpses, Nurgal will stop summoning zombies and start "draining the life from those around him" (the game emotes in red when he does this). He roots himself while casting this spell; if you fail to joust out of the way (and call your pets and/or merc off), Nergal will heal himself for 10%.
When done, head down the stairway at ( -95, -128, -108 ) /waypoint -95, -128, -108 and take a left to meet with Bigz the Big who will DISARM YOU and throw you in jail ( -191, -47, -240 ) /waypoint -191, -47, -240
Follow the hallway and drop down the hole in the floor.
Fight you way though (even though your DPS will be low due to your weapons being "confiscated" you should still be fine) to the chest containing your weapons ( -126, -145, -208 ) /waypoint -126, -145, -208.
Pick up the book a set of memoirs right next to the chest which is a house item and also contains lore about High Keep.
Grab the keys on the wall right at the entrance to the room ( -157, -147, -212 ) /waypoint -157, -147, -212. During the fight, you can open the cell doors to free the prisoners, some of them will help fight Zorin for a little while.
Zorin appears to have nothing special besides a speed boost when he says "I'll cut through you quicker now!" and when down to about 20% health will free all the jailed adds you didn't free. These adds leave once you have killed Zorin.
Stompus starts the fight with 6 Pickclaw conveyor operators. Technically Stompus doesn't hit very hard, but he hits very fast. He doesn't have much health (relatively speaking, he's still a boss).
At the beginning of combat, Stompus briefly becomes undamageable and runs to right in front of the Pulverizer, giving you a chance to clear his adds. Stompus will not move from his spot in front of the Pulverizer, so players getting swarmed by adds can just retreat out of his range and clear them.
a Pickclaw dredger are weak (96vv heroic) and cast a noxious potency and attack speed debuff. AOE these if possible while staying on Stompus.
Fighting out of Stompus' melee range but on the paved stone part of the floor results in Stompus casting a spell that throws you underneath the rock crushing machine. If it happens to come down on you, it's an insta-kill.
Periodically, the rock crushing machine will start to overheat (game will emote in red). Joust all the way off the paved floor back to the dirt floor to avoid getting one-shotted.
When Stompus looks up, rocks will fall from the ceiling. Either use an AE blocker or move back to a safe spot for a little bit. [/loc of the safe spot?]
After killing Stompus, collect his essence if needed and run through the Pulverizer right after it smashes then moves up.
Coward's option = (mine!)
Just stand off the paved area toward the entrance and range him down if you have a good hi (ish) dps ranged weapon. Just clear the adds off you from time to time and range him. Easy as that, no need to get even on the paved part and nothing touches you when he pulls his stunts!. I have seen in other walk thru's that he pulls you to him if you try and range him, but I have just done the fight and no problems, maybe if u try and range him while still standing on the stones that might happen, i do not know.
At the start of battle, Bolgin runs to a certain spot, roots, and summons several goblin adds. Burn the goblins. Bolgin will occasionally throw a flaming barrel at you, but it doesn't do too much damage.
Once the last goblin falls Bolgin will run to you. Tank n' spank for a while.
When a message says that "Bolgin drank too much of his potion!" Bolgin will become non-aggro briefly and stop attacking. If you hit him while he's in this state, when he re-engages he will summon adds, possibly one per incident of damage done to him while non-aggro. The adds aren't that tough - burn them down and get back on Bolgin.
At 10% health, Bolgin will say (out loud - he's voice acted) that you cannot defeat a God in his home realm. He begins hitting harder.