Hydross is the first planet of the Ossilon System, and is the first planet visited in the Core Contingency campaign.
Hydross is a world covered by a single vast ocean, a result of the planet's close proximity to its Sun. Because the ice caps had never formed, the planet has no landmasses. However, there are coral reefs in some areas that Kbots can walk upon, but cannot support structures. The seas of Hydross are also home to vicious, fire-breathing Sea Serpents that roam across the waves in search of prey.
Before the CORE's defeat at the hands of the ARM, they had hidden a CORE Commander upon Hydross as part of an ambitious contingency plan, who had lain dormant beneath the sea for centuries. When the ARM had, at last, completely eradicated the remnents of the CORE, the CORE Commander activated and set out to complete the Core Contingency plan: to find the Alien Artifact in the Ossilon System and use it to complete a Galactic Implosion Device, which would guarantee the total destruction of the ARM.
Because Hydross is completely covered by water, players are restricted to using naval units. Despite the lack of dry land, players are able to use naval series units in the place of structures that you could build on land, such as Underwater Metal Extractors and Floating Heavy Laser Towers. In addition to ships, players can also use seaplanes to provide air support for a their navy, and to strike at fortified naval bases protected by large coral reefs. Lastly, it is very important that players pay attention to their Metal economy, as Metal is hard to come by on Hydross, unless if there is a large amount of sunken ships to reclaim.