Here are the raids in Wrath of the Lich King except Vault of Archavon. To enter the Vault your faction need to control the Wintergrasp Fortress and there is not much action in Wintergrasp these days. I'll see if i get into it some time in the future.
Boss arenas is instances where it's simply a boss in a room and you fight it. They are the most boring to play but i guess the are very efficient to grind. There are three raid boss arenas in this expansion and i'm happy to say two of them spice things up.
Onyxia is the daughter of Deathwing and she rest in her dungeon when not doing evil things. This is a raid from the base game upgraded for wrath of the lich king. Stroll in, wake her up, cut of her head and then display it in Stormwind. First Nefarian and now Onyxia, we sure kill Deathwings children.
Good thing that Deathwings is dead or this might turn into a our problem in the future
Crusaders' Coliseum: Trial of the Crusader
Another arena fight that start out bland but ends with a suprise visit from the Lich King and a fall down into the Nerubian empire. Bit tiresome slog to get there but at least there is something new in the end.
The Lich King can not arrive fast enough
Eye of Eternity
The final battle against Malygos, the blue Dragon Aspect. The fight takes place in his own plane of reality and start out as a standard boss fight on a floating platform in the void. In the second phase mages on floating disc fly in and attack. In the last phase Malygos destroy the platform and a red dragon picks up each player and the fight turns airborne. Nice.
Stop spitting on my dragon
Chamber of Aspects
Below Wyrmrest Temple is a chamber for the Dragon Aspects to meet. It have a private area for each aspect and two of them have open portals that make it possible to visit. Borderline boss arenas but they have more then one boss.
The Obsidian Sanctum is the black dragonflight area of the Chamber of Aspects. Inside there are eggs from the twilight dragonflight. It is a dragonflight created by magical experiments on dragon eggs. The other dragons don't like it so lets go in there and kill the younglings. It is guarded by a black and three twilight dragons. They are spead out so it is possible to take them one by one. For extra challange start with the twilight dragon. The black dragons and all other creatures will then run to help him.
You have wings to leave that island you know
The Ruby Sanctum is the area for the red dragonflights. The black dragons did not like when someone made omelette of their eggs so they sent out a revange mission. The sanctum looks like a very relaxing green area with a small lake and a few very angry dragons. To mix it up they have one twilight and three black ones in here.
A grown up twilight dragon, off with his head
This is a dungeon floating above the Dragonblight zone. It used to be found above the Eastern Plaguelands in the base game but it have now moved to Northrend. I was not cool enough to visit it in the base game so let's go inside now. Did not start well with me failing to find the entrance. One google later i was inside and it's a large raid. Split into four wings where you have to kill a boss in each one to open up the way to Kel'Thuzard, the final boss. He was once a member of the Kirin Tor until he choose to go all dark arts. We all done that as a mage from time to time but your never go full dark arts. Then you need to die. Again in his case as he is a lich.
This green slime must be a health hazard
A titan installation that is also the prision of the old god Yogg-Saron. Like always the evil from the old god has corrucpted the ones around it so the titanic watchers need to be beaten into submission.
Train to the madness of the old god
The final fight against the lich king. Start at the base on the tower and fight your way to the top. Includes a short trip on the alliance ship Skybreaker. The lich king is not that hard but he have a attack that can knock you of the tower and i got to enjoy the fall once.