The King is a friend card used solely by Riku in Kingdom Hearts: Chain of Memories.
This card will summon King Mickey, healing Riku slightly, stunning and hurting all enemies for a short time, and restocking Riku's deck. Stocking these cards will allow you to use the only sleight you can as regular Riku, MM Miracle. It increases the amount you are healed and the damage done to enemies. It is one of the few ways Riku can heal himself, the other being the Oogie Boogie enemy card.
Using this card along with two Soul Eater cards while Riku is in his normal form will trigger the Holy Burst ability (where Riku and King Mickey go back-to-back shooting balls of light at the Heartless).
Using this card along with two Soul Eater cards while Riku is in Dark Mode will trigger Inverse Burst, which is about the same as Holy Burst except that Riku shoots balls of darkness.
