Old man Merlin
Merlin the Magician is a magician who resides in the realm of Camelot. He is King Arthur's primary sorcerer, though he tends to do his magic in private, leaving Morgan Le Fay in charge of public magic duties. Merlin is one of the most powerful sorcerers in Camelot, his only rivals being the Ice Wizard of Winter and the Dark Wizard of Mordred. Merlin has many abilities, his most notable ones being immortality and shape-shifting. As an immortal being, Merlin isn't affected by time, and so can smoothly transition between time periods. He is very difficult to recognize when he changes form, but likes to turn into knights. Merlin always signs his messages with an M, and he likes to write messages on unlikely things like leaves and shells. Merlin has an immortal penguin named Penny that he loves very much. Merlin initially doubted Jack and Annie due to their age, but after giving them various tests beginning with turning Morgan into a mouse, he accepted them as his apprentices, especially when they restored joy to Camelot. Recently, Teddy and Kathleen, two young enchanters Merlin has helped train, have taken charge of many of his missions.