Hogyoku Shard

The Hogyoku Shard is the only Legendary-tier material documented in the game, and its flavor text sells the weight: 'A glowing shard that pulsates with power...'. At 2 wt it is also literally heavy - twice the inventory weight of most materials.

Its documented usage covers two crafts, both high-stakes. First, it is an ingredient for the Hogyoku Fragment, a step on the path toward the game's wish-granting Hogyoku economy. Second, it is the backbone of the Hollow Soul recipe - 3 Hogyoku Shards, 4 Dark Essences and a Soul Chain - the item that upgrades a Menoscar or Adjucar into a full Vastocar with a fourth trait and Resurreccion weapon access.

Be careful with naming: the game has three similarly named items. The Hogyoku Shard (this page) is the Legendary crafting material; the Experimental Hogyoku Shard is a Rare consumable that rerolls your weapon; and The Hogyoku is the Mythical wish item. Only this one goes into crafting recipes, so check tooltips before selling or trading anything with 'Hogyoku' in the name.