Shadowblend is a passive ability that Spies possess in the multiplayer mode Spies vs Mercs in Tom Clancy's Splinter Cell: Blacklist. This ability allows Spies to literally become invisible in the shadows, increasing their stealth capabilities against Mercenaries.
The Shadowblend is a passive ability for Spies, meaning that it is always active, and every Spy class has access to it automatically. With Shadowblend, Spies are able to shift into a state of invisibility in the darkness. In light, however, this effect is disabled and flashlights from Mercenaries disables this effect. This may have been implemented to prevent players who are playing as Mercenaries to adjust their lighting on their television screens in order to better see Spies in the dark.