Medivh's staff - [Atiesh, Greatstaff of the Guardian] - can be used to teleport players to the front gate of Karazhan.

Everyone in the raid needs The Master's Key to be able to enter the instance.

The key can be gotten by following the following questline (Starts just outside Karazhan, with an Archmage of the Violet Eye (48,76)):

Atiesh Portal just drops you outside; it doesn't actually take you into the instance.

There is a quest to get keyed; this is an Onyxia style key, not UBRS; everyone has to have it.

No, using it just ports you in front of where the gate currently is. It doesn't port you somewhere special behind the gates or the door, in fact porting there in BC just gets you pwned by a ton of lvl 70 mobs if you're 60 :\

In order to enter Karazhan, you need to meet 2 conditions.

1. You are level 68 or above.
2. You have “The Master's Key,” which is currently sold by a vendor in Shattrath City.

To enter Karazhan you need the masters key. The key is obtained by a long quest chain given by an NPC outside the tower. A simple kill quest is first and there are a few follow ups. Later you are told that the key is broken in three pieces. Each piece is in a level 70 instance or raid instance that you need to go and retrieve. E.g. Shadow Labyrith, Coilfang Res, and Tempest Keep.

"[1. General - Ironforge] NoLifeNoob: have atiesh, will port nubs to kharazan 100g, pst