When the Battlegrounds debut, you will be able to collect quest loot and trophies off of players you kill. For example, if you are a Horde player and kill an enemy PC, you will be able to take from them their blood. Not only will this be a trophy of your victory, but in the Battlegrounds, amassing the blood of your enemies will have an awesome and powerful effect. If you and the other players on your team bring enough enemy blood, and by that we mean hundreds, to your side's head shaman, he will begin a ritual to summon an immense elemental, which will then march methodically into the enemy camp to destroy it. Likewise, for the Alliance side, bringing enough trophies to your head spellcaster will call an equally powerful being to your side's aid.