Each Ground and Character unit in your build zone gets "Reserves: This unit does 1 damage to one of your opponent's units in the Ground or Character arena. Play only during your build step."
Keywords
Reserves
Reserves: [Ability]: A layered, static ability that means, "The following ability works while, and only while, it's in the build zone." The granted ability remains to be the ability of its type. (For example, activated abilities granted by Reserves may be disrupted.)