Lord Kuruku is a puppet come to life. He constantly changes colors and size, though shades of red is the color he usually is the most. The shape is is the most is usually a round sphere. He has wavy bushes of hair that lay on either sides of his face, that often shoot out straight behind him when he is flying or if he is extremely angry when he is shouting. He pretty much looks like a highly demented and abstract male rendition of a classic witch. As a puppet, he is a small marionette with holes for eyes, a short, round, pole nose and has either a simple mouth or big chin (his mouth changes looks, depending on what part of the film he is shown in).
Lord Kuruku is a powerful, incredibly evil being, contrary to his goofy appearance (and that is what makes him so creepy). He is not possessed by a spirit, but rather he came to life by his own will which was made possible by the mysterious power of the sun.
Lord Kuruku is a very psychotic character who will use his magic to cast spells, to blast, kill and injure. He almost always is grinning and laughing while enjoying his evil works. He spends his days creeping around his castle on Nightmare Island, checking up on Toby, enjoying himself by swimming, lounging, playing with his toys and enjoying his evil intentions and plans. His castle is made entirely of living puppets, wooden-like figures that were once humans and other living creatures. His toys are also what use to be living creatures, now transformed. He turned them into these basically inanimate objects by his magic. He has an apprentice of sorts, a young human man named Toby, which is ironic when he hates all humans. Toby does his master's work of turning creatures into living puppets in exchange to learn more magic tricks from his master.
Lord Kuruku was a puppet in a "former life" if you consider him alive as a puppet. An old wizard and cruel woman who came to own him or got their hands on him used him improperly, so that his marionette strings become entangled. Even though undoing or replacing the strings would have been easy, they instead didn't bother with repairing him and instead simply threw him away like some unwanted garbage. They threw him away into some body of water, and from there he floated to the End of the Earth, where all unwanted thing eventually end up, brought in by the ocean/sea's currents.
At the End of the Earth there is only one small spot of sunlight, and it only shines for a few moments every day. This place where the sun shines is where Kuruku ended up, and after a few hundreds years of this, he came to life. The seemingly lifeless puppet moved, sat up and looked around. But the moment Kuruku awoke, he became unbelievably consumed by rage and anger that was pitted at the world and especially humans, because of his bad treatment in his "previous life". He then left the End of the Earth to take his revenge on the world. From there he crafted his plan to make all living creatures into living puppets, to become the lowly, and basically building blocks of his castle. He plans to enslave all living creatures and to take over the world, while building the largest castle on the face of the Earth.