Eye of q'bthulhu

Eye of q'bthulhu or eyes are items that can allow you to forge shadow or higher in a standard forge.

obtaining
the hardest thing.
 * 1) Trading
 * 2) loot collect weapons relic or higher
 * 3) the tome
 * 4) kill shadow giants, invaders, piñatas, etc
 * 5) shadow cache
 * 6) chaos chest

What is a shadow cache
they are special items only obtained by going into a shadow tower. If you are in normal you just get shadow shards (from vaults) which is a crafting material for it. Hard or ultra and you get them from opening a shadow tower vault.