When cast on living party or raid members, the soul of the target is stored and they will be able to resurrect upon death.
If cast on a dead target, they are instantly resurrected. Targets resurrect with 60% health and 20% mana.
The shadows will grant you another life; try not to waste it this time. — Pidge Filthfinder (TCG)
Soulstone is a core warlock ability learned at level 18. It creates a [Soulstone] that stores the targeted player's soul (or the warlock), allowing that player to resurrect. If the spell is cast on a dead player, that player is instantly resurrected.
Notes
A warlock may only soulstone one target at a time.
If the stored player dies, they will be offered the opportunity to reincarnate on the spot, or to be released as a ghost in the normal way. Soulstone resurrection may be used in combat.
Use of a Soulstone is on a 15 min cooldown, and creates a 15 min buff.
Patch changes
Patch 3.3.0 (08-Dec-2009): The cooldown on this spell and duration of its buff have been lowered from 30 minutes down to 15 minutes. Cannot be used in Arenas.
Patch 2.1.0 (22-May-2007): Soulstones can no longer be used on targets not in your party or raid. In addition, the soulstone buff will now be removed if the target or caster leaves the party or raid.
Patch 1.2.0 (18-Dec-2004): Reduced the Soul Shard cost from two shards to one shard.