#0 - March 19, 2009, 8:48 p.m.
http://i12.photobucket.com/albums/a225/ssba/immortal2.jpg
Keep in mind that they've been playing around with this achievement on the PTR a couple times now, so anything from this current iteration is subject to change.
Recap from Bornakk:
-2nd attempts in the same reset will not count, only first try
-Can be done over multiple resets
-Algalon is not apart of this achievement, which is intentional
-Titles: Champion of Ulduar (10 Man), Conqueror of Ulduar (25 Man)
-Naxxramas Immortal/Undying will not change, this is for Ulduar only