Hidden is a keyword ability in Shadow Era introduced in Call of the Crystals.

Hidden causes any hero or ally with the ability to become untargetable while hidden. In contrast to Stealth, this ability also protects from being targeted by ability cards and not just from attacks. Some cards also are able to hide attachments.

As of version 3.71 (September 2019), Hidden became a deprecated mechanic and was removed from cards it formerly appeared on.