Regeneration of Soul Shards was very limited. The Soul Shard is refunded if the detonation is successful. (Affliction only) - Applies to all enemy targets upon detonation.- Increases the crit chance of Searing Pain by 100%, and subsequent Searing Pain spells by 50% for 6 seconds.

- Increases total health by 20% for 8 seconds.

- Increases movement speed by 50% for 8 seconds.Summon Demon - Instantly summons minion.Their usage was similar to the current system, empowering the following spells:

Soul Shards were removed as items and changed into a secondary resource for all warlocks, up to a maximum of three. The Soul Shard resource mechanic as it appeared in Cataclysm 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.

Blizzard introduced soul bags, larger than average bags (similar to ammo bags), to help warlocks with the increased load. 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. They were generated by using on an appropriately-leveled mob. 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. 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.

Diablo 3 red soul shard wiki