A Strong Card is used to boost the power of your animal's 3 attacks.(Guts, Technique, and Power). It generaly has a green color scheme. The power boost varies for each card. Strong cards are needed to enable an animal to invoke "Gold Change" when using their best attacks. This is done by raising the level of the best attack of an animal by 5 stages. Additionally, some Strong cards also give aura effects to animals. Different Strong cards work better for different animals.