Spirit Shard

Spirit Shards are a PvP currency dropped by bosses in the Auchindoun instances when the player's faction controls the five Spirit Towers in the Bone Wastes.

Source
Spirit shards will drop from bosses in the Auchindoun instances when the player's faction controls the five Spirit Towers in the Bone Wastes. They can be looted by all party members (like heroic mode tokens and most quest items).

Drop rate is determined by instance, heroic mode does not affect the amount:
 * Mana Tombs - 1 per boss
 * Auchenai Crypts - 1 per boss
 * Sethekk Halls - 2 per boss
 * Shadow Labyrinth - 2 per boss

Gathering
Spirit Shards can be easily and effectively farmed by repeated partial runs of the Auchindoun instances. For example, a competent group of level 70s can run halfway through Sethekk Halls and kill Darkweaver Syth in just about 10 minutes, garnering 2 Spirit Shards apiece as well as Syth's normal rare loot.

Rewards
Players can use the shards to buy Terokkar Forest PvP Rewards from:
 * Spirit Sage Zran in the Allerian Stronghold
 * Spirit Sage Gartok in Stonebreaker Hold