The title is far from finished, though. Developer Arkane Studios has been working on a wealth of DLC which could reignite interest in the alternate history thriller. Today, the base game will receive a free update with two new modes: Story and Survival. The former is for players who might have struggled with Prey's ferocious difficulty, or simply want to explore and experience the ending. Survival, meanwhile, adds a trauma system and other difficult mechanics for veteran and 'hardcore' players. If you fall off a balcony, for instance, or get hit by the alien Typhon, you might break a leg or start bleeding out.

A new, paid DLC package called Mooncrash is also coming out today. It's a side story which, as the name implies, takes place on a lunar base called Pytheas. The facility has gone 'dark,' however, and it's your job to find out exactly what happened. You're cast as a spy on a nearby satellite that's able to simulate, or relive, the events leading up to the collapse. The new mode was inspired by indie roguelikes, or more accurately roguelites, such as Darkest Dungeon, Rogue Legacy and Risk of Rain. It's a genre typified by multiple runs, or lives, and randomized elements including enemies, items and level design.

At first, your task is to explore the base, upgrade your character and survive. During each run, you will be battling a corruption meter -- a breakdown of the simulation -- which makes the typhon evolve and heightens environmental hazards such as fire, blackouts and electrically charged puddles. As you explore the station, you will slowly unlock new characters with unique abilities and Neuromod skill trees. Joan, for instance, is an expert engineer who can repair, fortify and summon turrets. VJ, meanwhile, is a weapons specialist with the muscle to open unpowered doors.

"What we have here is like, something that's clearly descended from the immersive sim genre," Ricardo Bare, lead designer at Arkane Studios said. "It's a first-person action game, and it has roguelike elements, but it also has some storytelling elements that Arkane is known for mixed in with it. So it's this unique hybrid beast, I guess."

The ultimate goal is to help all five characters escape the lunar base. To succeed, you'll need to slowly build up the crew and combine their different abilities. You might start as the engineer, for instance, and find a broken door that leads to the escape pod hangar. If a horde of Typhon is lurking inside, it's best to unlock the door and move on, knowing that VJ can fight through and hopefully escape later on. When you switch to VJ, though, it might be better to find Joan's body first and pick up any equipment and resources she dropped.

Mooncrash will introduce two unlockable companions: a robot operator and a shapeshifting mimic. The operator is essentially a packmule that can ferry your loot to other characters. The mimic, meanwhile, will scurry through rooms and corridors tagging Typhon that have shapeshifted into everyday objects. There's also a new enemy called the Moonshark, which responds solely to sound and movement. The blind Typhon will burrow underground and try to surprise you from below; it's a devastating attack, but one that can be learned if you're able to find the corresponding Neuromod.

If the corruption level gets too high, or you run out of characters, you can choose to reset the base. The general layout will remain the same, but the content in each area will change. A laboratory might be pristine, pitch black or on fire. A door to a scientist's office could be open, damaged or protected by a keypad that can only be hacked by the engineer. Each session will, therefore, be unique and challenge players in different ways. Speedrunning will be possible, but the randomized elements should make it difficult for fans to create and follow meticulous walkthroughs.