The mount part is not totally my idea, got it from browsing the official wow furoms. The achievment idea though I came up with myself working last night.
Achievment: We are beasts!
achievment description: Defeat all the bosses of Naxx(10), archavon, sartharion(and his drakes) and malygos with less then 7 players(less then 17 on heroic) in the raid.
achievment reward: Title: The Beast...example-Sinbland, The Beast-, along with the mount Reigns of Red Corehound(10man achievment) and Reigns of The Beast(25man raid achievment...this mount will have the skin of The Beast from black rock spire)
ok so tell me what you think of this idea...I welcome trolls as well because negative criticism is fun...but would like some serious answers as well
edit-also tell me if the numbers should be lowered to less then 6 and less then 16 respectively....also this is just like a rank above to the dedicated few achievment...just like other achievments rank up such as the profession achievments and the undying part 2 in ulduar