Lady Blaumeux is one of the Four Horsemen (the final encounter in the Deathknight Wing of Naxxramas).

Her and Sir Zeliek are most likely the last two of the Four Horsemen that your guild will end up taking down as they are the hardest to DPS (position wise).

Lady Blaumeux deals moderate physical damage to your tank, but also drops a Void Zone every 12 seconds. The void zone deals 3500-4000 damage every 1second that a player is standing inside of it, and it also stays active for ~90 seconds. She will cast this under any player that is within 45 yards of her (including the tank) so players must be ready to move every 12 seconds (or when your mod tells you a void zone is incoming). The damage from the Void Zone is shadow damage, so it can be resisted from some Shadow Reisistance, or it can be absorbed (partially) by a Greater Shadow Protection Potion (https://classicdb.ch/?item=13459).
- Some information taken from http://www.wowwiki.com/The_Four_Horsemen

One of the 4 riders (last death knight wing bosses) very powerful AoE irresistable shadow damage, beware!

edit: yeah she's hot

The items are in a chest for the Four Horsemen
https://classicdb.ch/?object=181366

This is one of the Four Horsemen, the final encounter in the "Deathknight" (south-west) wing of Naxxramas. More information can be found at http://www.wowwiki.com/The_Four_Horsemen.