This skill, used by high level mercenaries, allows them to cleverly ambush their foes. When used successfully, their target is stunned by the sheer surprise of the attack, and the mercenary does a huge amount of damage for their first strike. The target will also fight less effectively for a brief period after being ambushed.
Sometimes the target will see the ambush coming and the plan will backfire, as the mercenary is taken aback and stunned for a short time themselves.
Targets that are wary (if they have been ambushed before or if they are particularly low on health) cannot be ambushed.