Hook: Lord Magog holds the Horn of Destiny and the players' group consists of one Sword Bearer (or one person with the potential to become a sword bearer).
Line: The Horn of Destiny is calling to the player, giving him visions and dreams in an attempt to convince the player that they should be linked.
Sinker: The Horn of Destiny is kept in Lord Magog's Great Tower and needs to be retrieved before the character can link with the artifact. This can lead to all kinds of interesting adventures as the players try to gather enough resources to be able to get in and then there's the actual retrieval of the artifact.
If you don't want to be this mean to players, then you can modify this slightly to something in L.A. under the Nightlord's control (but not inhabited by the Nightlord).