It seemed that some readers still weren't very familiar with the Cthulhu Mythos. I'll occasionally upload information about the Cthulhu Mythos characters appearing in this work, starting here.
Tsathoggua was one of the Great Old Ones in the Cthulhu Mythos created by American novelist Howard Phillips Lovecraft. Created by Clark Ashton Smith, he was also known as the "Sleeper of Ngai" and the "Toad God." Tsathoggua descended to Earth from Saturn and lurked beneath the dark abyss of N'kai. He was usually depicted as an enormous black creature with the features of both a bat and a toad, his eyes perpetually half closed in apparent drowsiness. Some accounts also claimed that he could change his form at will.
"Although I had never seen an idol of Tsathoggua before, I recognized him effortlessly from the descriptions I had heard. Potbellied Tsathoggua was squat and stout, his head resembling a monstrous toad rather than a god. Short fur covered his entire body, making him look like both a bat and a sloth. His two globular eyes were half open, giving him a sleepy appearance, and the tip of a strange tongue protruded between his thick lips."
-Clark Ashton Smith, "The Tale of Satampra Zeiros"
Tsathoggua Tsathoggua was one of the Great Old Ones in the Cthulhu Mythos, created by Clark Ashton Smith. He first appeared in Smith's "The Tale of Satampra Zeiros," written in 1929. However, because that work was not published in Weird Tales until November 1931, Lovecraft's "The Whisperer in Darkness," published that August, marked Tsathoggua's first official appearance. The two writers portrayed Tsathoggua differently.
Tsathoggua was a primordial deity who came winging in from the Outer Universe. According to legend, he was a Great Old One who descended to Earth shortly after its birth from Saturn, then known as