When your opponent's build step starts, roll a die. If you roll a 5 or 6, your opponent loses 1 build point, and you gain 1 build point.
Pay 2 Force Ambush 4
Keywords
Ambush
Ambush X: A layered, activated ability that means, "If your opponent deploys, moves, or puts a unit into this arena, this unit does X dice of damage to that unit." Each Ambush can be used once per instance of a unit being deployed, moved, or put.
Hidden Cost
Hidden Cost X: A selective, static effect that means, "As long as you have a number of build counters on this card equal to X or the unit's current build cost (whichever is less), you may complete it anytime by paying Force for the remaining build cost, if any." Effects and stacking rules may reduce the build cost. You do not need to pay Force if the build cost is within the Hidden Cost integer. You can deploy it to the build zone. Hidden cost can only be played if the card is partially built and has the required number of build counters on it. You may use Hidden cost anytime, even during any Play-or-Pass chances not reserved for re-roll, damage prevention, or disrupt POP chances. If there are a number of build counters on the unit equal to or greater than the Hidden Cost integer, you do not need to pay any Force. You may not use Hidden Cost to deploy a Pilot to a unit.