Reserves: , Pay 1 build point Roll a die. If you roll a 5 or a 6, you gain 3 build points. 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.)