Attuned rings were released with Heart of Thorns. Attuning a ring will supply one additional Agony Infusion slot on an Infused or Ascended ring. Rings that are both Infused and Attuned have two Agony Infusion slots, plus one default Infusion slot.
Attuned rings are crafted at the Mystic Forge. Attuned rings can be crafted from infused or non-infused rings.
Warning: When you craft an attuned ring from an Ascended or Infused ring, any upgrades that were on the ring that was used as an ingredient will be lost. The upgrades can be saved by using an Infusion Extraction Device before crafting. Even though the Infusion Extraction Device will make the Ascended or Infused ring Soulbound, the Attuned ring will still be Account bound after the crafting is complete.
List of attuned equipment:
Attuned Lost Seal of Usoku (Infused)
Attuned Royal Signet of Doric (Infused)