The Contestants are the most dangerous of the vanilla factions.
They are not a true faction and have no blocks of their own, instead they are a collection of ships built by the beta-testers. They can vary greatly in color and build style. The Contestants are aggressive, agile, and use their weapons better than the other default ships. They have an asteroid-style base as their reproduction point and are signified on the galaxy map with a megenta color.
The Contestants are not a playable faction.
Blocks
The Contestants have no blocks of their own. They are the ships built from other playable factions (mainly Terran).
Ships
Most of these ships are from the early beta-tester tournaments before Reassembly was released. In the default campaign they are generally small ships that occupy the Contestant regions. However, players can also experience them if they use the TEST button in the ship constructor.
Most of these ships are under 6000P. A few of them are so large that they do cannot normally spawn in the game at all.
Notes
The original Anisoptera tournaments can be viewed here.
There is actually a faction 17, which is just the Contestant ships with no colors.
Add Your Own Contestants
The Contestant ships are in the extra_ships folder in the game’s data directory.
You can add your own ships to the Contestant faction by creating a mod that includes an extra_ships folder containing your own ship designs. See Modding for more info.