Mr. Stone was an alien Mi-go who appeared in Peter J. Evans' 2013 novel Feeders from Within. He was called Mr. Stone as his human associates required a name to reference him with; as Mi-go have no need for names, he settled upon the first object which caught his attention, a stone.
History
Mr. Stone was one of the Mi-go present in the cave encountered by Mark Harrigan's squad during the Pancho Villa Expedition in the Sierra Madres. Although grievously injured in the conflict with the soldiers, he managed to reconstruct both himself and the barely-alive squad leader, Sergeant Johnathan Orton, using parts from the dead troopers and Mi-go.
Travelling to the United States with Orton (who had changed his name to Phillip Avery), the two allied themselves with the Silver Twilight Lodge with the aim of completing Mr. Stone's task, which was to reassemble the Shard of Panestes in order to travel unmolested into Tsathoggua's domain.
Finally locating the missing pieces, Mr. Stone transferred Avery's mind into a Mi-go brain cylinder to grant him the immortality he had been promised, before opening a portal to N'kai.
Reaching N'kai, Mr. Stone attempted to locate the Feeders from Within, a species of parasitic creature which would cause madness and destruction on Earth. The expedition was thwarted by the arrival of Mark Harrigan and Diana Stanley, who destroyed the Shard and in doing so awoke Tsathoggua, who consumed Mr. Stone before the others escaped.