Buffing

Soul Shard is a required reagent for many warlock spells like health stone and soul stone. Warlock players need to make sure they always have enough soul shards in the bag.

A Soulstone can be used to store one target's soul, if a warlock dies while his/her souls is stored, he/she will be able to resurrect with a certain volume of health and mana. By this feature of the souldstone, a warlock makes constant attacks in battles and survives well in the wild.

A healthstone

A healthstone is subordinate to a soulstone in that it can only be used to instantly restore some health exactly like a health potion.

Fel armor:

Surrounds the caster with fel energy, increasing the spell power. In addition, you regain 2% of your maximum health every 5 second.

Spell stone

Spell stone can be used as a main-hand weapon, it increases damage caused by periodic spells.

To summon

To summon a companion like Felguard or Void Walker, a warlock also needs Sould shard.