Dark Dragon-Slaying Bullet (BT10-121) - Rise of the Unison Warrior

[Counter:Play] If you have a yellow Unison Card in play : If the Battle Card being played has an energy cost of 4 or less, it has its skills negated for the turn and is played in Rest Mode.
[Permanent] If all of your energy is mono-yellow, you can activate this card's [Counter] skill from your hand without paying its energy cost by choosing 2 other cards from your hand and discarding them.