A Green Requiem has a smooth, conical body that is a light shade of green and has a Heartless emblem is emblazoned on its chest. The top of its body flares outward and forms a jagged "collar" below the Heartless's spherical, pitch black head. It also wears a conical, orange hat that has a jagged brim, a peach band, and a thin, curled tip. Like many Heartless, the Green Requiem has glowing yellow eyes. Its seemingly useless feet sport three small, thin toes.
Like other Heartless in its family, the Green Requiem's name is comprised of a color—in this case, green—and a musical term—in this case, a requiem, a piece of music composed to honor a dead person. This is fitting, given the Green Requiem's ability to heal other Heartless.
Green Requiem utilize Cure magic, and are resistant to all other forms of magic. They tend to fly rather high, just out of Sora's reach. Like their relatives, Green Requiem are most common in Wonderland, or at least once the Hollow Bastion Keyhole is revealed. A common place you can find them, after you seal the Hollow Bastion Keyhole, is at the High Tower, on the other side of the giant steps. A few of them will be surrounding a Defender, and you can kill those, leave the world, come back to the same spot and kill them again. They are also seen in Monstro in Kingdom Hearts Chain of Memories.
A good way to defeat Green Requiem is to equip High Jump and Aerial Sweep, then jump and attack. It is also important to note that they absorb all magic spells. In Kingdom Hearts: Chain of Memories, do not equip attack cards with passive elements, like Lionheart and Photon Debugger, as using these cards to attack a Green Requiem will heal it. The best way is to simply use the Kingdom Key.
The best place to find many Green Requiems is at the cliff area in the Deep Jungle after passing through the Camp. This is only after you have beaten Hollow Bastion for the second time, and is a very good location for obtaining synthesis materials.