Hero ItemsDust of Appereance - Purchased at player-built shopsHumans
Crystal Ball - Reveals a targeted area. Invisible units are also revealed by the Crystal Ball's effect.
Sentry Wards - Drop Sentry Wards to spy on an area, and reveal invisible units.Flying MachinesOrcs
Mortar Teams - Flare
Towers - Magical Sentry. This is an upgrade at the Arcane Sanctum to allow you to see invisible units using your Towers. The Humans have the easiest Invisibility detection.Far Seer - Far SightUndead
Witch Doctor - Sentry WardShades - Shades see invisible units.Night ElvesHuntress - SentinelNeutral
Priestess of the Moon - ScoutBeastmaster - Hawk