The Elemental War is an event mentioned in the Sonic the Hedgehog comic series and its spin-offs published by Archie Comics. It was a war that took place some point after the Ixis Resurgence on Light Mobius.
At some point in the past, the Ixis Resurgence occurred, followed by the Elemental War. During this crisis, Tikal was forced to bind herself to Chaos in an effort to control him. The result was the creation of Tikhaos. The new being was extremely unstable, and the Tikal portion would lose control if provided with too much Chaos energy. Thus, Tikhaos was subdued and quarantined in the catacombs beneath Castle Mobius.