Randolph Carter is an antiquarian and one-time student of the Miskatonic University, who is familiar with several supernatural things including the Great Old Ones and a realm called the Dreamlands.
A melancholy figure, Carter is a quiet contemplative dreamer with a sensitive disposition, prone to fainting during times of emotional stress. But he can also be courageous, with enough strength of mind and character to fight and defeat the horrific creatures of the Dreamlands
Based on clues from various stories, he was probably born around 1874 and grew up in and around Boston. At the age of ten, he underwent a mysterious experience at his great-uncle Christopher's farm and thereafter exhibited a gift of prophecy.
He is the descendant of Sir Randolph Carter, who had studied magic during the reign of Queen Elizabeth I of England. Sir Randolph had then emigrated to America and his son Edmund Carter later had to flee the Salem witch-trials. Carter also had an ancestor involved in one of the Crusades, who was captured by the Muslims and learned "wild secrets" from them. Within the League universe, he is also the grand-nephew of John Carter.
During his younger years Carter frequently visits Dreamlands, where he has multiple allies. His best known adventure in the dream lands was his Dream Quest to find the city of Kadath. At the age of 30 however, he loses his ability to go to the dream lands, until he finds a mysterious Silver Key that allows him to re-enter the dream lands and other realms.
Role in the LoEG stories
Randolph Carter has a large role in the story Allan and the Sundered Veil, in which, during his search for Kadath, he wanders into an astral plane where he meets his long lost great-uncle John Carter, the British adventurer Allan Quatermain, and The Time Traveller. He is recruted by the Time Traveler to help him fight off the forces of the Great Old Ones, but he turns out to be of no help to the team because of his lack of fighting skills and his nervous personality. His grand-uncle John is clearly disappointed in him, stating that the Carter clan is no longer what it used to be. When the time machine of the Time Traveler is broken and the four heroes are stranded in a chrono-crystal aleph, Randolph Carter sees several visions of his own future, including a vision of Arkham. Shortly afterwards Randolph Carter's astral form leaves the dreamworld again and returns to his body in the natural, waking world.
Randolph also has a small role in The New Traveller's Almanac, in which he encounters Allan Quartermain and Mina Murray during their visit to the Miskatonic University (an event already foreseen by Allan when he looked into the Aleph). Both Allan and Randolph recognize each other, but can't quite recall from where, having apparently forgotten their past adventure with The Time Traveller. Together they encounter an Eldritch Abomination.
Randolph Carter was created by horror writer H.P. Lovecraft, and is one of the few human characters who appears in more than one story by Lovecraft. All stories that feature Randolph are part of the Dream Cycle and by extent the Cthulhu Mythos. Randolph can be considered an alter ego of Lovecraft himself.
In their respective source material, Randolph Carter and John Carter are not related since they belong to different authors. The idea of them being family comes form Alan Moore.