Strata is a subterranean world that exists thousands of miles below the Earth's surface. It is populated by a variety of races, who live in isolation of the surface world, but are very much aware of the effects that surface dwellers have on their planet.
Strata evolved from the dessicated husk of a so-called "Astronaut God" whose corpse crash-landed on Earth eons ago, perpetuating the Ice Age. The Astronaut God's body was contained inside a special suit that protected it from the rigors of space travel, but also managed to preserve its DNA as well as a computer record of the last years of its life. The Astronaut God's blood flowed like lava, seeding the veins of the Earth, ultimately evolving into the Stratan people. 
The Stratans possess a rare metallic ore known as Quixium, whose transmutative properties enables them to genetically alter any one they choose. The Stratans select an individual to act as their champion in defense of the planet and use the Quixium to change their physical form as well as provide them with geomorphic powers. To date, there have been three such champions who have hailed from Strata, all of whom used the code-name Terra. The first was Tara Markov, who was also the sister of Markovian super-hero Geo-Force. When Tara Markov was killed during the "Judas Contract" affair, she was replaced by Tara Markov II, a woman whose physical body was altered to resemble that of the first Terra. This Tara Markov also suffered a brutal death at the hands of Black Adam during "World War III". The current champion of Strata is Atlee who, while physically different from her predecessors, still possesses the means to affect the Earth's geomorphic field.
Shortly after Atlee adopted the mantle of Terra, opportunistic industrialist Richard Faulkner discovered Strata and sought to take advantage of its wonders for his own ends.