The great Cthulhu of H.P. Lovecraft's Cthulhu mythos. Describe as one of the great old ones, the creature is imprisoned under a sunken city to once again rise and cause chaos on earth. Cthulhu is described as having an octopus like head, huge wings, and standing taller then any building. For my version, I gave it more of a squid shaped head for a more distinctive shape. Instead of many tentacles near the mouth, I chose 3 to keep the design clean. Normally many people give Cthulhu clawed arms, but I've always imagined it to have tentacle arms.
Death or the Grim Reaper and sometimes the Angel of Death, is a popular character of Halloween. Death as an actual living entity has been around since the Middle Ages as a skeletal figure carrying a sickle. Sometimes he can be tricked or bribed in order to stay alive, but it is also thought that he severs the soul and body creating death. For my design, I was inspired by Charon of Greek Mythology, who users the dead to the plane of Hades. Death has a black toga instead of a completely black robe, I also wanted his head to float high above his actual body so he could hid his form while meeting the newly dead. The scythe made of vines from the under world that holds his blade. Over all, I tried to reinvent the character to be more associated with Hades.