Dieyno the Warlock, Eye of the Graeae, is a Unique Ghastly Seraph found in the Plague Tunnels Level 1 in Act V of Diablo III. He may spawn when the cursed chest is touched (alternatively, his brothers Ennyo or Pemphrido may spawn).
In combat, he has Molten, Orbiter and Waller affixes.
Like his brothers, this monster is named after one of the mythic Graeae Sisters, Deino. The title is a reference to the sisters having just one eye to share among the three.