- You may be looking for the imaginary planet.
Sir Galahad was a Knight of the Round Table.
He was the illegitimate son of Lancelot and of Elaine, Daughter of Pellam. The Round Table itself called for him to be knigted, though he was but a young man at the time; this occurred in the presence of Donna Noble and the Tenth Doctor, the latter of whom was posing as Merlin at the time. He wielded a sword that was actually a fragment of the Druse, like Arthur himself and several other Knights of the Round Table.
Although his parentage was obvious from his resemblance to Lancelot, no one at the Round Table dared to mention it; (PROSE: Legends of Camelot) he was the subject of "bullying gossip" in the castle, however, and sought to make up for it by being the most noble knight possible. Bedevere thought him to be pleasant company, finding that he had in common with King Arthur himself a capacity to "mask the sad emptiness under the surface with outward confidence". However, his general reputation was that of an "insufferable goody two shoes".
Galahad, alongside Bedevere, Agravaine and Gawain, was one of four knights whom Merlin once sent on a four-day journey to slay the Morch'aliach in its cave. Galahad objected when Agravaine elected to cause a rockslide that trapped the beast in its cave but did not slay it; suspecting that the entity would survive, Galahad argued that it was "unchivalrous" to leave the threat for future generations to deal with. (PROSE: A Honeycomb of Souls)
According to legend, Galahad would eventually find the Holy Grail and ascend to Heaven. (PROSE: Legends of Camelot)