'Nerocite' is a very effective fuel mined in the Dune Sea. It is clear the Xylvanians are quite fond of it, as the objective of campgain 2 of Battalion Wars was to destroy the Xylvanian Necrocite mines before advancing into Xylvania itself. However, the later objective was delayed because of the sudden invasion of the Solar Empire by Xylvania.
Nerocite was also the backbone of the Iron Legion having it's entire military based off the substance. Nerocite is extremely volatile allowing the Legion's weaponry to be very powerful but with some side affects such as their Flame Veterens that were said to be driven crazy by their own weapons
Nerocite is probably based off of oil from the real world, because Nerocite has the same function and is found in large quantities in warm, desert areas.