Power Cards are either actions your monster takes, or upgrade for your monster to make them better at smashing Tokyo, or other monster. Price of each Power Card is stated on the top left corner of the card. Power Cards are purchased with Energy (symbolized by Energy Cubes).
Each Power Card have their unique effect, stated on each card.
Keep cards have an ongoing effect. They are placed face-up in front of you until the end of the game (unless something tells you to do otherwise). Some Keep cards require Tokens to measure their effects, in which case find the correct Tokens and use them as instructed on the card.
Discard cards have an immediate effect. Resolve the effect and then discard the card. You may not hold on to a card marked discard to use it later.