During Pre-game~Selections, mark a point on the Battlefield with a Gateway Marker: it must be within~24 of your Deployment Zone, outside the opponent’s Deployment Zone, and more than 1~from any Impassable Terrain.
One use only. At the start of a friendly Magic Phase, if the bearer’s unit was allowed to move in the preceding Movement Phase (ie. it is not Shaken, did not Ambush, did not fail a Charge, is Unengaged, etc.), you may remove it from the Battlefield and immediately place it back on the Battlefield with Ambush (friendly Gateway Marker, that was not placed during this Player Turn).