Bloodbane likes to summon elementals and swarm, so you will need a psionic to spook out elementals or this fight will be very difficult. Alternatively, you can use flash bombs or calm and blind elementals individually. You used to be able to fill his room with NPCs (from the shop in town) but this method has been foiled by the Immortals and is no longer a viable trick.
Additionally, Bloodbane likes to cast momentary darkness near the end of the fight. Be prepared to deal with this by either: 1. waiting it out, 2. bringing lots of dispel area options with you (a high level wizard would be best, several negation orbs, etc), 3. an archon with a redemption, or 4. a psionic who can cancel illusion (preferred method if you are trying to get someone the mark.)
We strongly recommend SETTING AUTOLOOT OFF for this fight, as some of the loot that may be dropped is difficult to get off of your person!
Spell up as normal.
After doing the normal dispelling and spelling up, your first objective is to fill his form with elementals. Have a psionic spook the elementals north until his forms full, or cast calm when he summons elementals and blind each one out of combat. Alternatively, you can target each elemental and blind it in-combat, calming after each one to take it out of combat. He will randomly cast swarm as well, until his form is full. When he swarms, itís best to cast calm and kill the swarmed mobs. Then keep going at it until his form is full.
Once his form is completely full and spooked north, the fight is much easier. He hits pretty hard, itís best to fight him when he has his 2h sword in his hand as this will cut back on the damage he does. The easiest thing Iíve found with him is to cast cure light on yourself every single round. He will cast counterspell every chance he gets. This will keep him busy trying to counter you instead of him casting offensive spells on you. If you keep doing this he will eventually die.
Another option is to have a psionic cast cancellation summoning. I tried this a few times but found it cheaper, and a lot less annoying, to just spook elementals until his formation is full. He had a nasty habit of swarming wasps which proceeded to para me.
Once Bloodbane gets down to about 15% health, calm the fight and have your psionic cancel illusion. This will prevent him from successfully landing momentary darkness.
If you are attempting to get the Mark of Valor for a lower level person (180 or mid 4th class), at about 3-5% health (monitor the form's damage output before deciding when to calm), then calm and unform the person getting the mark. Be prepared to cope with the momentary darkness, especially if you do not have a psionic. Spam healing spells out of combat on the mark-getter, and have the person getting the mark spam damage. It is important that the mark-getter can out-damage Bloodbane's regen. Be diligent about this. You may need to have one archon stay in combat until he is at 1% then flee and quickly unform (this is tricky, but possible) in order for the lower level to land that killing blow.
'a waxed piceous scroll' - shadow door 'a set of overlord armor', a level 190 body armor, casts sanctuary. 'the Bloodbane combat gloves', a level 200 hand armor, +2 ar. 'the mighty sword of Bloodbane', a level 201 two-handed-sword. 'the skull of Riga', a level 200 armor. - do not loot this item unless you know for sure you want it! If you accidentally looted it, see A Down-On-His-Luck Sorcerer for removal. 'the Overlord's helm', a level 80 head armor, +2 courage. 'the Overlord's necklace of protection', a level 200 jewelry, casts level 100 armor. 'a Bloodbane Family ring', a level 120 jewelry. 'a diamond gemstone', a level 10 warp-stone to the Proving Grounds. 'a summoning pentagram', a level 10 artifact. 'a blank spellbook', a level 75 treasure. 'a bracer of destruction', a level 140 armor. - +4 or +5 accuracy.