Source: Volo's Guide to Monsters

Armor (shield), rare

A mind flayer skilled at crafting magic items creates a shield of far sight by harvesting an eye from an intelligent humanoid and magically implanting it on the outer surface of a nonmagical shield. The shield becomes a magic item once the eye is implanted, whereupon the mind flayer can give the shield to a thrall or hang it on a wall in its lair. As long as the shield is on the same plane of existence as its creator, the mind flayer can see through the shield's eye, which has darkvision out to a range of 60 feet. While peering through this magical eye, the mind flayer can use its Mind Blast action as though it were standing behind the shield.

If a shield of far sight is destroyed, the mind flayer that created it is blinded for 2d12 hours.