The Savage Land was created by the alien Nuwali at the behest of the other-dimensional, nigh-omnipotent aliens known as the Beyonders. The Beyonders sought to observe the process of evolution under relatively controlled conditions and had the Nuwali set up a number of game preserves on several planets. One of these planets was Earth during the Triassic period where the Nuwali chose a valley in Antarctica surrounded by active volcanoes where they installed a number of advanced technological devices in order to maintain a tropical climate. The aliens then stocked the area with all manner of Earth life over the following several millennia. The Beyonders, who are not only other-dimensional and energy-based but also experience time non-linearly, eventually grew bored with the experiment and the Nuwali stopped maintaining the Savage Land during the late Pleistocene. However, the technology that allowed the pocket of tropical climate was left running and many species which became extinct in other areas of the Earth continued to thrive within.
In more recent years the Savage Land was rediscovered by Lord Robert Plunder who took back a sample of the metal known as Vibranium with him. This mysterious metal had the ability to produce vibrations which would liquefy all other metals. Fleeing from those who sought to steal this discovery Plunder took his eldest son Kevin with him for a second trip into the Savage Land. Unfortunately the elder Plunder was killed by the local tribe of Man-Apes. Kevin survived, thanks to the timely intervention of the widowed sabretooth tiger later known as Zabu. Abandoned in the Savage Land Kevin grew to adulthood there with his sabretooth companion and eventually became the lord and protector of his adopted home.