With that out of the way, the Obsidian Sanctum is home to Sartharion the Onyx Guardian and a trio of black drakes. They look more purple, perhaps lavendar, but we'll stick with black. The Drakes are mini-bosses, only with a few minor mechanics to learn and understand. Killing each one of them removes an ability from Sartharion himself, who you attack last. There is some trash between mini-bosses, but it's minimal.
The bosses are currently somewhat undertuned, but they're not going to be particularly difficult for a reason. Downing them one by one is not the challenge of this raid zone. Like Zul'Aman, it has an additional challenge for you to tackle after you've killed everything on "easy mode." You can pull Sartharion before all of the Drakes are dead for bonus loot. That bonus loot includes a Black Drake Mount
Beating Sartharion and the mini-bosses individually is pretty easy. All of them have one or two gimmicks, but they're just that. Gimmicks. However, you can pull Sartharion with as many drakes up as you'd like. One, two, three, or none of them if it's your first few jaunts into the raid. With each drake you add, there's another mechanic or two to keep track of. We're talking portals to different dimensions, damage shields, continuously spawning adds, things like that. With the more drakes you bring into the mix, the more complicated and dangerous the encounter becomes. Yes, they all need to be tanked in some way, too.
Each added drake in the mix equals one bonus epic amongst your loot. When you bring in the third drake? Your reward is the Black Drake Mount, an epic flying mount. Very cool. Very, very cool. It seems the 25-man version may give a different drake, too. A Twilight Drake. A white dragonflight? Seems so!
I really like the design of this dungeon, and building upon that aspect of Zul'Aman. The dungeon isn't just a straightforward jaunt where you beat it once, you can beat it forever. If you beat it once, you can challenge yourselves further for greater reward next time you go in. That rush of, "Hell yeah, we won!" is not just a one time thing in this dungeon. That rush is renewed with each step of the challenge you defeat. When this raid is tuned properly, it's going to be a great, great place for raids to experience. Best part is? The place only takes about 30 minutes once you've gotten the whole thing down.
Blizzard has a lot of one or two boss raid dungeons, so that'll be a fun little thing to occupy a night of raiding. Instead of spending an entire night in one dungeon, you can dedicate a night to traveling around the world taking these guys out. There's still stuff like Naxxramas of course, but this is a fun change of pace. Here's hoping it continues well into endgame, and aren't only entry level dungeons like Gruul and Magtheridon.