Create Spellstone is a warlock Demonology spell that creates a Spellstone. Originally a pseudo-relic that occupied the wand-slot which allowed warlocks to dispel all magical debuffs on themselves and increasing spell critical strike rating, Spellstones are now much like Wizard Oils that are applied to the Warlock's One-handed weapon after the Echoes of Doom Patch. A single use of Create Spellstone (which uses a Soul Shard as a reagent) will create a Spellstone with 5 charges. Each charge can be only used on the weapon of the warlock who created it.
Spellstones have a checkered past of use. Originally, the spellstone was equipped in the off-hand slot, was consumed on use, and granted a buff that absorbed spell damage. It was almost completely unused by the Warlock community, who largely wielded staves. In the 2.0.1 patch, Spellstones were equippable by the warlock in the wand slot, improved spell critical strike rating and could remove magic debuffs. The Spellstone was considered by many warlocks to be a critical conjured item for PVP and PVE alike since the 2.0.1 patch. However, Warlocks differed over the benefit over having a spellstone equipped in place of a wand, since the cooldown on the magic-removal use was 3 minutes. The crit bonus was a passive ability from equipping the stone and could be increased by [Master Conjuror]. The crit bonus was roughly equal to +1% at the level each rank is learned. The Echoes of Doom patch changed the Spellstone to its current form.
Patch 3.0.2 (2008-10-14): Spellstones were changed to their current form, akin to 5 charges of Wizard Oil per Spellstone.
Patch 2.3.0 (2007-11-13): The text on Spellstone was changed to say it dispels instead of removes.
Patch 2.1.0 (2007-05-22): These abilities will now be sorted in rank order in your spellbook.
Patch 2.0.1 (2006-12-05): Prior to this patch, the spellstone was equipped in the off-hand slot, was consumed on use, and granted a buff that absorbed spell damage. There was a corresponding [Improved Spellstone] talent to increase the damage absorbed.
Patch 1.3.0 (2005-03-07): Equipping Spellstones will now improve your chance to get a critical strike with spells.