Auchindoun used to be a giant temple/burial site for the Draenei until the Horde came through and set up a fortress, they left and basically every other race in Outlands started squatting in a wing of the temple. The Mana Tombs are currently being occupied by ethereal grave robbers.
Weirdly, the lore of the place is essentially, “These guys are robbing the tombs! Kill them so that these other guys can rob the tomb! Of course, the game doesn’t spell that out for you, but that is pretty much how it goes.
Degree of Difficulty: Hard
Personally, I think Mana Tombs is the singular most annoying instance in the Burning Crusade expansion. Even when soloing it now. Both the first and last rooms have to be cleared of all mobs before the boss, or they all pull. A lot of the mobs have the typical annoying BC gimmicks. Mana drain, gouge, lots of shadow damage, it’s kind of mind numbing.
Pandemonius is an elemental who pulls his entire room. The actual fight is not that difficult though, once you isolate him. Tavarok is a rock giant who hits very, very hard and has stuns and AoEs, but you get to fight him by himself in the hallway. Shaffar has adds that need to be taken out which distracts the DPS making the fight take a lot longer than it might otherwise. Also you need to clear his room.
Access to the Heroic mode can be purchased from the Lower City quartermaster in Shattrath at honored. A quest will let you summon the demon boss Yor. Upon completion of that quest, you will be able to summon Yor at any time in Heroic mode.
Recommended for Levels: 63-66
Mana Tombs is annoying for sure. None of the fights are very fun, and the whole time you go through, you’ll probably be waiting for it to be over with. But the XP gains are pretty great and some of the drops are good though all you’re really doing at this point is holding steady until you get to Northrend.
Solo it for the achievement, but you’ve got better things to do between 60 and 70 than waste time killing every single bit of trash in an outdated instance. That having been said, if you get it in a random, just know what you’re doing, put your head down and soak up some XP.