Ensidia, now of Tarren Mill-EU, reported today that they have captured the world-first A Tribute to Immortality. Considered to be one of the most difficult, if not most difficult, raiding achievements currently in the game, A Tribute to Immortality requires a perfect run of heroic Trial of the Crusader-25 with no player deaths and all 50 attempts remaining. The reward for pulling this off is the Crusader's Black Warhorse (Alliance version here), but I wouldn't expect to see too many of these running around in the near future.
I'm most impressed that they managed to get through the heroic version of Faction Champs without losing anyone, although -- as Mackzter acknowledges on the news release -- the achievement "involves a bit of luck." Congratulations to Ensidia, and best of luck to all the guilds out there working on this as well!