The unit can enter stealth mode. While stealthy, it cannot be targeted with spells and ranged attacks. The unit leaves stealth mode once it attacks, counterattacks or shoots missiles. Enabling this mode and moving while stealthy consumes additional stamina.
In addition, starting a turn while stealth mode is on depletes 5 stamina, which quickly drains all stamina and renders the unit using it useless. However, this skill can have its use when you need to avoid death of a precious unit by ranged attack just before finishing a battle or getting out of range.