Stormheim Pit is a 20vs20 resource race battleground for level 110 players. Located in Stormheim, the objective of the battleground is to hold orbs of lightning for as long as possible, accumulating points but taking (and dealing) more damage the longer you hold it.
http://wow.gamepedia.com/Temple_of_Kotmogu#Orbs
• Best compared to Temple of Kotmogu; it's exactly the same layout and size but there is no lower level part. Imagine a large Roman Gladiator Pit (like a Colosseum), except the map is rectangular instead of circular. Vrykul spectators gather in the stands to watch the fight. • On either side of the map are where the Alliance and Horde players spawn (like in Temple of Kotmogu). • In the middle of the map, going from the top of the longest side of the pit to the bottom of the longest side of the pit there are four Lightning Orb's that can be picked up (imagine where the ball is placed in Soccer, but along that same line there are three other balls and they're spread equally apart). • Once you pick up a Lightning Orb you start to accrue Victory Points for your team at the rate of 5 points every 10 seconds per Lightning Orb that you hold. • Every 10 seconds that you hold a Lightning Orb, you take an additional 15% damage, deal an additional 10% damage, and receive 5% less healing. • If you die while holding a Lightning Orb, the Lightning Orb will be given to the player that killed you. If nobody is alive when you die while holding a Lightning Orb, it will be dropped at your feet (i.e a Player #1 DoT's Player #2. Player #2 kill Player #1. Player #2 is given the Lightning Orb that Player #1 possessed. Player #2 dies. Player #1 isn't alive to receive the Lightning Orb so it's dropped at Player #2's feet). • Graveyard's are in each corner of the map near the walls. You'll respawn at the nearest graveyard. • Berserk and Healing buffs are close to the walls. • Goal is to reach 1500 points.
Basically, imagine a World of Warcraft team juggernaut version of Temple of Kotmogu, where instead of having to stand in the one area to gain points you can be anywhere on the map to gain them. And instead of having to manually click the Orbs once they respawn in the one location, you get them when you kill the Lightning Orb holder.