For kicks, the team decided to run it on Elite - 'oh joy' I thought. Let me just say that the instance was pretty intense, enough to write about it, which I don't normally do for most other in-game material. That said, I learned a lot about it which I feel could be shared, assuming you don't mind some spoilers.
Note that this isn't a full walkthrough of Therakiel's Temple as I've only run it once. I just want to give what information I can to help others and to help explain just how good this instance really is.
Firstly, you NEED a tank and some healing, perhaps even a rezzer. The reason for this is that the bosses can do some crazy damage, especially if someone forgets to block, which will likely kill them. I highly suggest against a random pick-up group (PUG) for this run, as anyone attempting to PUG it probably doesn't know the fights either and is in for some nasty surprises.
Most of the mobs are simple groups of critters you can take down normally, but there are some exceptions. For example, the Immortal (a vampire mob) turns into a ball of mist and cannot be killed unless it is staked. You can make stakes from the nearby coffins in the area.
There is also a theme that runs through the instance, that of light and dark. You must constantly pay attention to this, as the map becomes somewhat of a maze... let me explain. Littered throughout the areas are large bubbles, some light and some dark. If you enter a bubble you get a buff associated with its type. If you try to enter a bubble with a similar type to what you have just previously entered, you will be forced back and take damage. This means that you must constantly alternate moving between light and dark bubbles. To do this, you'll often have to find alternate routes to get where you want to go and have to backtrack to get the bubble you need to pass through the next bubble. This was probably the most aggravating part of the entire instance, short of Therakiel himself.
It should alswo be noted that every party member needs to pick up a divine mirror from the entry to the instance. Continuing with the light and dark theme, there are statues that block your progression throughout the instance that can only be destroyed by beams of light. There are also light sources scattered about the areas, but are usually never near these statues. What you must do is form a chain from one party member to the next, streaming the beam of light from its location to the statue. This part was actually kind of fun and really helped to build teamwork as you had to bend the light around corners and whatnot.
As for the bosses, let me give you a quick rundown of each. Again, this is only from what I've learned after running the instance once, so I might be missing some things. Feel free to post a comment and fill in any blanks!
- Valerian Scarlet is a sorceress and the first boss you meet. She's a simple tank and spank from what I could tell.
- Black Fang is leader of the Dogz and sounds a bit like Arnold Schwarzenegger. He also seemed like a tank and spank boss.
- Baron Cimetiere is the voodoo guy. When he blocks, STOP ATTACKING or he will do massive damage to you!
- Dracul is the vampire leader. He must continually have the "staked" debuff on him at all times, or will become immune to your attacks.
Secondly, Theraiel has a super attack where he spins his sword. When you see him do this, BLOCK! If you don't, he will do an insane amount of damage and kill you regardless of how far away from him you are. Watch for this to happen several times throughout the fight.
Thirdly is Therakiel's eyebeam attack. I noticed this didn't kick in until at least halfway through the fight. Anyway, he will target a player or pet with the eyebeam attack and shoot white light from his eyes. You cannot block this attack, as it goes through blocking. When you are hit, you are held - make sure to inform your party members as they can free you! To do this, one must go to a light source and bounce light to you using their divine mirror. You don't have long to save a teammate when this happens, which makes for a somewhat frustrating situation. The only other way to stay safe from Therakiel's eyebeams is to stand in the light source itself, which may or may not work depending if you can get him close enough to the light to do so. Remember there are only two light sources and they aren't very big, meaning some players have no choice but to stand outside unprotected.
I hope this post helps others trying to learn about Therakiel's Temple - I know from searching online that I could find little information about the fights, which made me very apprehensive about running it in the first place. I know this isn't a comprehensive walkthrough but at least this should help!