In the world of Siren Apocalyptic there is no big difference between the monsters and the heroes. The only difference between them is that the monsters have all the features of a boss. They have several attacks, special abilities and weapons, but they are not very smart and usually get killed easily. In contrast, the heroes have a clear aim and almost no weaknesses - they do not need a lot of preparation and can attack with surprise. They also have several skills and special abilities that can protect them from harm, but do not allow themselves to get damaged. They do not need much preparation either, since they can just do anything at any time.
In the Siren Apocalyptic Unblocked game world there is this thing called the 'Shimmering Mirror'. This mirror somehow changes the appearance of the people in order to blend into the environment, thus making the enemies seem more human. When the heroine enters the Shooter's world, she gets a fatal injury thanks to a shark that attacks her and a weird looking alien. In the field of medicine, the doctor realizes that the alien is actually a living being and therefore, the scientists managed to create a new life form called the Revenants.