Douglas Birely, born in Culver, California, was once a geneticist employed by a private research company in his home state. He specialized in the effect radioactivity has on mutation. Birely went to his employers seeking clearance to experiment with live subjects, his hypothesis being the target would aquire super powers by means of mutation, but was denied. He proceeded to move foward with his experiment anyway, choosing to illegally experiment on himself, later resulting in him being fired. Birely's hypothesis, however, proved to be untrue as he contracted a lethal skin cancer. To stop the effects of the cancer, Birely created devices that he wore under a synthetic stretch fabric. With his new life-sustaining costume came his newly adopted identity as supervillain, Dr. Demonicus.

Dr. Demonicus learned of a higly radioactive meteorite that had entered Earth's atmosphere and landed in the Aleutian Islands. He came into possession of the meteorite and dubbed it the Lifestone. The Lifestone had the ability to create monsters by mutating living organisms and with it Dr. Demonicus created Ghilaron, Centipor, Lepirax, and Batragon, being also mutated himself by the meteorite.

Establishing a base on one of the Aleutian Islands and organizing a group of criminal troops, Dr. Demonicus began to raid oil tankers, using both his troops and his mutated monsters. His operations were halted when his monsters were defeated by Godzilla. Dr. Demonicus was overcome by Gabe Jones and taken into custody by S.H.I.E.L.D.

After aquiring freedom once again, Dr. Demonicus allied himself with an alien, the Myndai, Maur-Kon, who provided him with his space station base. Dr. Demonicus assisted Maur-Kon against  the Shogun Warriors with his genetically and robotically engineered monsters, Cerberus, Starchild, and the Hand of Five. The Shogun Warriors were victorious over his creations and stopped his attempt to launch a meteor strike at Earth from his base. Dr. Demonicus was again taken into S.H.I.E.L.D. custody.

Dr. Demonicus returned to supervillainy again when he managed to capture Godzilla, mutating him and controlling him. He had Godzilla attack the West Coast Avengers. Dr. Demonicus then salvaged Iron Man's original armor and used it to continue his assault but was foiled by Anthony Edward Stark.

Under Dr. Demonicus, the Pacific Overlords were created. They were defeated in battle by the West Coast Avengers and Sunfire.

From the floor of the Pacific Ocean, Dr. Demonicus raised a land mass north of Hawaii. He declared himself as the the ruler of his island-nation, Demonica. Dr. Demonicus was rejected in an attempt to have his nation recognized by the United Nations. Demonica sank to the Pacific floor once again, Dr. Demonicus escaping.

Dr. Demonicus was among the 43 to escape the Raft. He was recruited into the Hood's organized group of supervillains and was later defeated by Doctor Strange in a battle with the New Avengers.