Soul Shards



Soul Shards are a unique secondary resource available to warlocks, displayed in the user interface beneath the player's health and mana bars. Warlocks can have a maximum of five Soul Shards, which slowly regenerate out of combat and regenerate in combat through certain spells. Soul Shards have been around in some form since early WoW and have a long history as a secondary resource for warlocks in general.

Generated by

 * Agony
 * Conflagrate
 * Doom (talent)
 * Drain Soul (talent)
 * Immolate
 * Incinerate
 * Shadow Bolt (Demonology only)
 * Soul Fire (talent)
 * Soul Strike (talent)
 * Summon Demonic Tyrant (rank 2)
 * Summon Infernal
 * Unstable Affliction

Consumed by

 * Bilescourge Bombers (talent)
 * Call Dreadstalkers
 * Chaos Bolt
 * Grimoire: Felguard (talent)
 * Hand of Gul'dan
 * Malefic Rapture
 * Nether Portal (talent)
 * Rain of Fire
 * Ritual of Doom
 * Seed of Corruption
 * Shadowburn (talent)
 * Summon Demon
 * Summon Felguard
 * Summon Felhunter
 * Summon Imp
 * Summon Succubus
 * Summon Voidwalker
 * Summon Vilefiend (talent)
 * Vile Taint (talent)

Regeneration BfA (8.1.0)
Out of combat, Soul Shards regenerate over time up to a maximum of three. In combat, up to a maximum of five Soul Shards can be generated through Agony and Unstable Affliction.. Each tick of Agony has a chance to generate a shard, and Unstable Affliction will generate a shard if active at the time of a mob's death.

History
Soul Shards have been a warlock resource since early WoW, and their use has been revamped many times to make them more streamlined with the warlock playstyle and improve quality of life.

Vanilla
Soul Shards were originally items held in the player's inventory and were required to cast many important spells, including summoning any demon besides an imp, summoning other players, and creating Healthstones. They were generated by using Drain Soul on an appropriately-leveled mob.

Raiding warlocks tended to carry large quantities of them to prepare for nights of progression as resummoning their minions and creating Healthstones would deplete their stores rapidly. Blizzard introduced soul bags, larger than average bags (similar to ammo bags), to help warlocks with the increased load. However, the inconvenience of having to carry dozens of Shards and the difficulty of replenishing them when already fighting a boss had the warlock community clamoring for changes to their design though they would remain largely unchanged for many expansions.

Cataclysm
Soul Shards were removed as items and changed into a secondary resource for all warlocks, up to a maximum of three. Their usage was similar to the current Soulburn system, empowering the following spells:
 * Drain Life - Reduces cast time by 50%.
 * Summon Demon - Instantly summons minion.
 * Demonic Circle: Teleport - Increases movement speed by 50% for 8 seconds.
 * Soul Fire - Instant cast.
 * Healthstone - Increases total health by 20% for 8 seconds.
 * Searing Pain - Increases the crit chance of Searing Pain by 100%, and subsequent Searing Pain spells by 50% for 6 seconds.
 * Seed of Corruption (Affliction only) - Applies Corruption to all enemy targets upon detonation. The Soul Shard is refunded if the detonation is successful.

Regeneration of Soul Shards was very limited. Out of combat, the warlock could use the spell Soul Harvest (old), which restored 1 Soul Shard per 3 seconds for 9 seconds on a 45-second cooldown. In combat, the only way to replenish shards was through Drain Soul and Shadowburn, a Destruction-only talent that restored three Soul Shards if the target died within 5 seconds. Both spells required appropriately-leveled mobs.

Since shard replenishment depended on the existence of adds, it meant that for single-target fights, a warlock would have only three shards to spend, no matter how long the encounter. Using Soulburn in conjunction with any spell that was not Soul Fire meant a decrease in DPS, punishing its use as utility especially after the release of Tier 13 granted 10% spell power upon using the two spells together. (The 4 piece set bonus has since been changed due to the revamp of the Soul Shard system for Mists of Pandaria.)

Mists of Pandaria
Mists of Pandaria gave each warlock specialization its own secondary resource system, with Soul Shards made into an Affliction-only mechanic. Soul Shards were changed to regenerate automatically outside of combat, although abilities such as Drain Soul were still useful for replenishing stores mid-fight. Mid-expansion patches saw an increase in the maximum number of shards from three to four.

Lore
Gul'dan needed soul shards containing draenei souls to properly command the smaller demons he summoned and to summon lesser demons Gul'dan's lesser warlocks must use a soul shard. The Lich King trapped Alexandros Mograine's soul in a soul shard, tormenting him in an attempt to break his will.

Fel energy consumes souls, hence, warlocks use soul shards. The foul crystal creates a link to the Twisting Nether.