Trojan Horse is a very interesting holding. As of Inquisition, it is the only holding a player may attach to an opponent's realm, and he must do this during phase 2 (just like any other holding).

Attaching this to an opponent's realm has three effects. The first and least is that every champion is at adjusted level -1. This actually won't help much, and more often will allow the defender to play the first card into battle.

The second is more useful. It allows any player (not just the one playing the holding) to attack the realm. Position and movement restrictions are moot, making realms like The Coral Kingdom (11/FR) very vulnerable. However, the second power does NOT remove requirements or non-movement restrictions. Therefore, realms like The Spiderfell (3/BR), The Ruins of Zhentil Keep (3/3rd), and Anytown, Anywhere (70/4th) are still as difficult to attack, and make a great defense against this card.

The final power is by far the best. The attacking player may choose who defends it. Therefore, this is an excellent way to be able to remove problem champions, like Tasslehoff Burrfoot (39/DL) or Necba the Wrathmaker (14/DU-chase).

This works particularly well with instant win champions to give the opponent no chance to win the battle. However, it should be noted that the defender doesn't need to defend, and can just allow the attacking champion to raze the realm, removing the holding.

Also, one could defend against the Trojan Horse by having all his realms have holdings, allowing no place for this holding to get played. However, one card to assure spoils of victory is a good card play.

Finally, the best revenge against someone playing this holding on you is to turn it back upon them by using Hallucinatory Terrain (42/FR).

This is a very good card for a combat deck that hates facing the unattackable realms.