Elemental manipulation is a technology mentioned in the Ancient universe. The Ancients ran an experiment to "create a completely viable ecological and social microcosm", which would then be transported to Terra and replace the original ecosystem.
They needed a central controlling unit to handle any unforeseen problems, and appointed Sheltem to be the Guardian of Terra. However, Sheltem felt that the colonization experiment was an "invading army", and did everything he could to undermine the experiment.
The experiment was instead launched under the guidance of Corak, who was sent to remove Sheltem as a threat and become the new Guardian of Terra.
The exact nature of the technology is not known, but it involved the use of the power of the Elemental Planes, and even the elemental lords themselves.