This is a fresh new idea and design, not much of a roleplay, although you could consider it like that due to the extreme amount of teamplay involved.
There are two sides, Aliens and Marines, and they must battle it out against each other.
The Marines rely on getting resources from building generators on steam ducts, and with their commander, researching new hardware for them to tech up. The marines themselves level up with every kill they get, allowing you to upgrade your weaponry and your armour.
The commander can buy upgrades and research new ways to fight back against the Alien Infestation, from buying new weaponry such as Flamethrowers, Plasma Rifles and Machine Guns to buying sentry guns or new suits such as a Exosuit.
The Aliens are somewhat the same, although they do not rely on a commander, they tech themselves by kills and evolve with that, as well as getting specie upgrades from placing eggs on steam vents, they can build seveal structures, like traps, hive sensors and various other equiptment to aid them.
Upgrades range from allowing facehuggers to climb up walls, to easy access ventilation systems or hide above a marine, ready to pounce or maybe a fade ability so when Drones are sitting still, they are hard to spot, before it's too late.
Well, it would not be a showdown of some of the greatest species in this universe, if they were not involved, they will be donation only, and only 3 predators will be allowed on at one time, this is enabled once one of the races is dominating another, donators can then become a predator and choose which side to help, they have a very big arsenary, and to stay alive, they have to use all of their survival skills, they arn't invulnerable, but they pack a punch, and a race which is has tech/evolved can easily wipe out the preadators.