Lore : The Brand of Cthulhu
Those most dedicated to Cthulhu's nihilistic cult will burn his brand into their flesh, often in a ceremony on the moonless night of the lunar new year, witnessed by the god's unblinking green stone idol.
A crude version of this brand has also been found tattooed onto cultists living on the Pacific Islands.
The Star Spawn
The Star Spawn are a pre-human, octapoidal race spawned from Cthulhu. Their physical form is dwarfed in comparison to their progenitor, though they themselves are still quite large. At a time in Earth's history, the Star Spawn waged a war again the Old Ones.