Nexus Crystal

Nexus Crystal is an ingredient for high level enchantments and a blacksmithing plan.

Source
Nexus Crystals are disenchanted from high level epic and rare items at the following probabilities:
 * Item level 56-60 equipment: 1x
 * Item level 76-80 weapons: 1x (33%), 2x (67%)
 * All other Item level 61-80 equipment: 1x (50%), 2x (50%)
 * Item level 66-99 equipment: 1x (0.5%)

Nexus Crystal as an Ingredient
Nexus Crystal is used in the following recipes:

Blacksmithing

 * Sageblade

New in Patch 2.2
 * Nexus Transformation

No longer needing Nexus Crystals as a reagent

 * Enchant Cloak - Dodge
 * Enchant Cloak - Greater Fire Resistance
 * Enchant Cloak - Greater Nature Resistance
 * Enchant Cloak - Stealth
 * Enchant Gloves - Superior Agility
 * Enchant Gloves - Threat
 * Enchant Gloves - Fire Power
 * Enchant Gloves - Frost Power
 * Enchant Gloves - Healing Power
 * Enchant Gloves - Shadow Power