Power Cards are a type of Battle Card used in the Ninjago: Spinjitzu Spinners game. They were first released in 2012 and can be identified by their border, which is green with a reptilian scale texture.
Like Metal, Golden, and Crown Cards, Power Cards are an overarching subtype of the card, and thus still have designations based on their effects (Confuse, Control, etc.). Their main feature is their SP cost; all Power Cards require an equal amount of SP in all four elements (Earth, Fire, Ice, and Lightning), which can make them difficult to use for certain characters (such as NRG Ninja) without the use of Boost Cards.
However, Power Cards tend to have powerful effects, and their SP costs rarely exceed 300 in each element (although one card, Card 115 - Opposition, has 400 SP in each), making them useful tools for characters who have decent SP in all four elements, but lack the SP for higher-power cards in any particular element.