Let's take a look at how to get to him, his abilities, and some simple strategy to defeat him.
Before You Go
Get the quest "Chamber of Secrets" from an Argent Dawn Emissary. There's one in Light's Hope Chapel in Eastern Plague Lands, and there are a couple in the capital cities. This quest can be shared with other raid members. After you've defeated Tenris you can pick up the quest item from his room to complete quest. Return the quest to either Light's Hope Chapel or the NPC you picked it up from.
How To Reach Tenris Mirkblood
Go into Karazhan and clear up to Attumen. Go up the stairs in the back of Attumen's room, right around where the repair guy is. You'll have to clear several sets of mobs. If you are in T5 gear or below, take your time. Most mobs are grouped up in packs of three to five. There are also a few roaming packs that you'll need to watch out for.
At the top of the stairs you can go right or left. While both will eventually take you to Tenris, going right is the quickest. Clear the rest of the mobs until you come to Mirkblood's door. Be sure to clear any mobs around the area that might be patting back and forth.
Do not open it until you are buffed up and ready to face him.
Tenris Mirkblood's Abilities
Blood Mirror – Damage suffered is shared with whomever is mirrored.
Sanguine Spirits – Evil red spirits that explode for around 6.5k to 10k damage, depending on gear.
He hits no harder than Attumen.
How To Kill Tenris Mirkblood
Have your tank open the door and engage Tenris. Drag him out into the hallway as far away from the raid group as you can. At this point let the tank get some good threat and start to DPS Tenris down. Two things are going to happen during the fight.
First, red spirits will appear. If you get close to one it will explode for around 6.5k damage. You'll want to avoid these. People are reporting that these spirits will grow in size and move towards people.
Second, Tenris will cast Blood Mirror. This spell will look like a gigantic red stream of blood flowing between Tenris and the person he casts it on. This person will take a large percentage of the damage done to Tenris as long as the spell is active, which is around 10 seconds. There are two things you can do to get around this. You can either heal the living daylights out of the person under the influence of the spell, or you can stop all DPS on Tenris. If you don't outgear the instance, stop all DPS while Blood Mirror is active. If you are special and have the abilities Feign Death, Vanish, Shadowmeld, Ice Block, or Bubble you can get of out Blood Mirror early.
After Blood Mirror is done you'll have a little bit of time to just do straight DPS on Tenris. The red spirits will continue to stack up, and most groups will find that you have to kite Tenris around a little bit to avoid getting swamped in the spirits.
Eventually he'll die, and you'll get some new loot!
- Arcanite Ripper – 2H Axe that also acts as a guitar. See the video above.
- Vampiric Batling – A bat pet, one drops for each member of the raid.
- Badge of Justice x2
Disclaimer: This is a new boss and while we're pretty darn sure of the information contained in this post, we will update it with any new information we come across.