Pay 4 Force Your opponent gains 5 build points and may spend them as though it were his or her build step. Then you gain 5 build points and may do the same. Play only when no unit is attacking.
The one spending build points may place build points on a face down card either already in the build zone or placed into the build zone from his or her hand. This does not create a build step and the players may not deploy or complete cards with build costs.