WoWDB

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. http://www.wowdb.com/items/22383-sageblade is the only true item left which requires nexus crystal. http://www.wowdb.com/spells/42613-nexus-transformation was introduced as a means for players to get some worth out of their stockpiles of these crystals. was introduced as a means for players to get some worth out of their stockpiles of these crystals.

edited for clarity