Dealing with the skeletons, the Ranger and the Warrior can jump. The Mage cannot.
Do NOT unlock the gates.
Enter sneak, jump one companion just inside the area and wait for the jump cooldown.
Exit sneak and move forward to aggro.
Teleport either the Ranger or the Warrior outside the room. Use the others to get a free shot on him from sneak.
Jump the initial companion outside and finish the first skeleton off, if needed.

The Warrior will jump outside and attack. Kill him. Then, enter and kill the Mage.

Blood the Historian however you want. Do NOT bless him!

The portal will open to access the chamber but not the one inside to the upper level. Jump, loot and take the portal to return outside.

Do NOT bless the Historian. Kill him FTW, XP and the loot.

A tip for anyone who might have trouble finding a source of blood (i.e. a Lone Wolf Party consisting of Fane and another Undead): utilising an elf's Flesh Sacrifice will create a nice little pool of it, which can be achieved by using Fane's Mask of the Shapeshifter.

Why do you even need blood rain if you can just bless the hellfire pigs and did anyone even figure it out without a wiki?

Create a blood surface then bless it. Worked like a charm for me.

You need to complete the puzzle so that you can get a "crumbling skull" to open another door.

When you remove the fire from him a portal opens to the Realm of Orobas. If you save him there's a portal inside Orobas that leads to a chest. The wiki saying there's no reward for saving him is wrong.

I doused him, blessed him, talked to him and he said he ain't given me s###t, and I got no XP for it. So that was pointless

I struggled a lot with him dying immediately once teleported into blood.. so I tried using human blood. That stopped him dying immediately

1. Blood Rain
2. Telekinese green poison plant next to him (he is undead and heals in poison, enough time now)
3. Bless

How the hell were we supposed to know that to put out hellfire you need to bless blood ??????