Prospector Loren at the Ulduar Archivum wants you to obtain Mimiron's Sigil.
For more information on obtaining Mimiron's Sigil consult the Archivum Console.
Mimiron's a clever one. His entire abode is rigged with some sort of self-destruction mechanism.
Unfortunately yer gonna have to race against it if ye want to get his sigil. Check the Archivum Console for more details if ye need them.