The Knight Ring (ナイトリング Naito ringu) is an accessory that first debuts in Fire Emblem: Genealogy of the Holy War. When equipped, this ring permits its wearer to use up their remaining Movement range after completing any given action. In this regard, equipping this ring is akin to assigning the Canto skill to a selected character.
Ch. 19 - Have Janaff or Ulki speak to Naesala in order to convert him into an NPC unit. Ensuring that Naesala's Raven subordinates are kept alive, let Naesala move up to Reyson to speak to him. Reyson will receive the ring after the conversation ends.
The Knight Ring, as it appears in the third series of the TCG.