Nexus Crystal used to be one of the materials necessary for a number of Enchanting spells but in Burning Crusade was replaced as a material with the level 70-equivalent, Void Crystals.
Sageblade is the only true item left which requires nexus crystal. Nexus Transformation was introduced as a means for players to get some worth out of their stockpiles of these crystals.
Nexus Crystal used to be one of the materials necessary for a number of Enchanting spells but in Burning Crusade was replaced as a material with the level 70-equivalent, Void Crystals.
Sageblade is the only true item left which requires nexus crystal. Nexus Transformation was introduced as a means for players to get some worth out of their stockpiles of these crystals.
edited for clarity