It seems that it can be used for a final blow somehow But it's a Normal Spell, so it's tough because the timing to use it is limited
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Compare the backs Check to ensure the colours match with an authentic card (especially the shade of blue) Fakes will have slightly darker or a lighter border Avoid cards with washed out backs No edge bleeding - the border should be separate Pokmon card backs have been the same for decades, meaning that comparing cards using the backs is a reliable way to check if a card is fake or not
Sets like the upcoming Blazing Vortex are expected to make a big impact on the meta, and as such, the cards going in Side Decks are likely going to have plenty of new additions
Every other timing rule for casting spells still applies: If the mayhem card is an instant, you can cast it any time you have priority that turn, but if it's a creature you can only cast it at sorcery speed (unless another effect gives it flash)
Any additional costs are paid as normal