I went ahead and did the quest, just to knock it out. Must say that it was very fun and I was able to nail the boss in my first attempt. He was pretty easy, nowhere near as bad as Nomad was. Just be prepared to run around a lot (go to the hot springs and get infinite run energy before the fight) and bring brews/super restores with a beast of burden carrying them as well. I didn't even need to use my BoB's supplies, but it's nice to have in case something goes wrong.
I used leech defense, deflect melee (when he was on the ground), deflect magic (when he was in the air), hot springs for infinite run energy, blisterwood polearm (obtained in the quest), BCP and tassets (thanks, Meg!), dragon boots, barrows gloves, neitznot helmet, war tortoise, saradomin brews, super restores, and glory ammy.
Make sure you turn game sounds on, because you need to listen for when he says things.
"Stare into the darkness." Turn around and face the opposite way, if you are meleeing, it is easiest to run to the wall and face away from him.
"Let the blood consume you." He teleports you into a pool of blood, just keep running away from it and he will follow you, just hit him when you're out of it. People say that luring him onto the blood and tanking him does quite a bit of damage, but I found this difficult to do because the blood disappears pretty quickly.
"Come, fiends, and aid your master!" He will summon two of his minions from either sides of the room, they walk really slowly towards him. Just kill them really fast, they have low HP. If they make their way to him, they will heal him, so try to kill them off as quickly as you can.
He also does an attack where he will fly up in the air and throw blood bombs at you. Just run around the room as much as you can, don't hold still. If you can manage to time things right, you can hit him while he's in the air and while you're dodging the bombs. He is weaker when he's in the air so you'll hit a bit higher damage on him, but if you can't time it right, don't worry. It's not worth dying over, just wait 'til he lands again and then you can attack.
In his mist form (final form), keep throwing your holy water out and lure him onto it. He will eventually die after doing this a few times. Just don't let him get too close because he does rapid magic-based attacks.
That's about it, really. As for ranging and magic, I'm not too sure what the best procedure is, but with melee I just described everything I did and it was pretty damn easy. Good luck!
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