Used as spies and familiars. The demon sees all with its large singular eye. Oculous demons find their ways into secret meetings and hidden laboratories, and other places that might interest their masters and take in everything with their all seeing eye.
They avoid combat and usually flee if discovered.
Oculous Demon D&D 5e
Small Demon Chaotic Evil
Armor Class: 13
Hit Points: 21 (3d6 + 3)
Speed: 25′ fly 40′
Str 8 (-1) Dex 17 (+3) Con 13 (+1) Int 12 (+1) Wis 14 (+2) Cha 10 (+0)
Skills: Stealth +7
Damage Resistances: Bludgeoning, Piercing, and Slashing from nonmagical weapons that aren’t silvered
Damage Immunities: Poison
Condition Immunities: Poisoned
Senses: true sight 120′ passive perception 14
Languages: Understands abyssal, telepathy 120′
Magic Resistance: The Oculous Demon has advantage on saving throws against magic and other magical effects.
Nimble Escape: The Oculous Demon can take the Disengage, Hide, Invisibility action as a bonus action on each of it’s turns.
Multiattack: an Oculous demon makes two claw attacks
Claw +5 d4+3
Invisibility The Oculous Demon magically turns invisible until it attacks or until it’s concentration ends, anything worn or carried also turns invisible.