RG Live WotLK 3.3.5a

When you click on the "Arcane Container" there should spawn a "First Fragment Guardian" that you will have to kill to loot the key (introduced in patch 2.0.8, before you simply looted it from the gameobject).

Source: https://www.wowhead.com/quest=9831/entry-into-karazhan#comments

steopes on 2007/02/16 (Patch 2.0.8)

After the last patch day 02.14.07, a guardian spawn when u open the chest where the fragment is, so u must kill the boss before grief the fragment.

- The First Fragment Guardian was spawning, however he was way out of position behind a wall. He should now be spawning at the Arcane Container and attack the player on spawn.
- Arcane Container should now properly despawn upon being used, preventing spam-clicking ---> spawning infinite amount of mobs.

Regards,
Despondency