The Toymaker once claimed to be the embodiment of one of the fundamental forces of the universe, much like the Guardians of Time. Whereas the White and Black Guardians personified the absolutes of morality, however, the Toymaker was the avatar of games and illusions, known as the Crystal Guardian.
Within his realm, the Celestial Toyroom, the Toymaker commanded immense powers, but they were limited by the rules he set for any particular game. He himself was immortal and invulnerable, and appeared capable of space and time travel at will. For some reason he chose to appear in the guise of a middle-aged Caucasian Human dressed as a Chinese mandarin.
During the course of a game, one of the players might die outright or they might lose, in which case, the Toymaker would have total control over their life and personality, perpetually. Apart from these children's games, the Toymaker sometimes played in person against his 'guests', most often games of chance such as cards or dice. There is evidence to suggest that if he was fairly beaten in such a game, the other player was allowed to go free, but if his opponent lost or tried to cheat he became another exhibit in the Toyroom. Such opponents included professional gamblers from the American west and Roman soldiers.
The Doctor first learned of the Toymaker, as a youth at the Prydon Academy. The data banks of the Time Lords described him only as a vague legend. The Doctor and his friends Rallon and Millennia, who like the Doctor belonged to a clique known as the Deca, investigated the legend, travelling to the Toyroom in a stolen TARDIS. The Toymaker was in a dormant, disembodied state at the time, but on their arrival he possessed Rallon and made Millennia into one of his servants. The Doctor defeated him, however, and the Toymaker allowed him to leave, knowing that he would become an even more worthy opponent given time to mature.
During the latter days of the Doctor's first incarnation, the Toymaker drew the Doctor's TARDIS back to his realm and made the Doctor and his companions play his games once again. This time the Toymaker arranged things so that even if they won, the Toyroom would collapse around them at their moment of victory, leaving him the consolation of being the only survivor. The Doctor was able to outwit the Toymaker again and escaped, leaving his realm in chaos. Rallon had been keeping the Toymaker's powers in check since he was initially possessed. He made the Toymaker abide by the rules of his games so as to allow the Doctor to escape. At the end of this adventure, the Doctor believed, incorrectly, that, since he had won, the Toyroom no longer existed.
The Toymaker discovered that after centuries of existence that Rallon's body was dying. He set about a plan to ensnare the Doctor again and hatched a complex plan to turn the Doctor's companions against him and absorb the Doctor as a new host. He was thwarted when Rallon forced himself to undergo multiple regenerations consecutively. The trauma expelled the Toymaker from his body. A projection of Rallon's potential future self merged with the Toymaker to ensure that the full powers of the immortal continued to be kept under control.
The Toymaker somehow managed to regain full control of his powers some time after this, and used them to lure a number of people into his domain, including the Doctor and his companions Ace and Hex . Working together under the Doctor's leadership, the group of victims were successful in defeating the Toymaker and imprisoning his essence in a doll (or so it seemed). Each of them ate a piece of the doll, dividing the Toymaker so that he would no longer be capable of using his powers. The Doctor then concocted an elaborate plan to keep control over the fragments of the Toymaker in the minds of each person in the group until the Toymaker would finally wither away forever. However, as this plan involved the Doctor forgetting having made the plan in the first place, the Doctor himself wound up short-circuiting it. In the end, it was revealed that the Toymaker had been in control all along, allowing himself to be absorbed into humanity so that he could "feel what it was like to lose". In the end, one of the people involved, the chessmaster Swapnil Khan, managed to trap the Toymaker in a perpetual stalemate in his own dimension, but not before the Toymaker had reduced everyone except the Doctor, Ace, Hex, and Khan's daughter Queenie Glasscock to wooden dolls.
Eventually, the Toymaker returned, trapping the Doctor in a replica of the village of Stockbridge. Here he forced the Doctor to play games for control of a reality-warping alien device called the Imagineum. The Toymaker's pawn on this occasion was a replica of the Doctor himself. The Doctor persuaded his double to turn against his master. With the Toymaker distracted the Doctor used the Imagineum to create a replica Toymaker, which he set against the original. A stalemate inevitably ensued. The Doctor destroyed the Imagineum and freed Stockbridge from the Toyroom. The Toymaker was trapped in apparently perpetual battle with himself.
The Toymaker once played chess against Fenric during the latter's imprisonment. For once the Toymaker found himself on the verge of being outplayed, but slowly realised that, in this case, playing for a stalemate would be a victory of sorts.
Another story tells that the Toymaker, now calling himself the Mandarin, appeared in Blackpool and, using a thrill ride, Space Mountain, as his base of operations, manufactured deadly video arcade games. He was stopped by the Doctor and placed in an impenetrable force field. Because the Mandarin's mental energy maintained the force field, the Doctor had set it up so that he could never escape it.