The Egg Pistons mk.II machine consist of an entirely mechanized room in Metallic Madness Zone with only two entrances. The room's ceiling and floor are equipped with gray and hollow pistons big enough for Dr. Eggman to reside within. These pistons are so closely packed that, together, they can fill out their entire room. Also, on the right side of the Egg Pistons mk.II machine's room is a red bulb-like generator for firing energy orbs.
Features and abilities
The entire room that makes up the Egg Pistons mk.II machine is one massive trap. Once someone enters, all exits close off, preventing any and all escapes. The room's pistons will then protrude from their surfaces for the purpose of squishing any unfortunate victims caught below them. Adding to the danger of the room, its red bulb-like generator can manifest energy spheres that will home in on any victim that manages to stay alive.
In Sonic Mania, the Egg Pistons mk.II machine was used by Dr. Eggman to combat Sonic, Tails and Knuckles when he managed to trap the trio in his invention's room while they passed through the Zone. While the heroes fought back against the Egg Pistons, the extensive damage they dealt to them eventually caused the machine to go haywire, making it much more dangerous. Regardless, Sonic and co. survived long enough to make the Egg Pistons mk.II machine blow up with Eggman inside it and escape to freedom.
Sonic Mania Plus
In Sonic Mania Plus, the Egg Piston mk.II was repaired. When Sonic, Tails, Knuckles, Mighty and Ray later passed through Metallic Madness Zone, Dr. Eggman trapped the group of heroes inside the Egg Piston mk.II in an attempt to eliminate them. While trying to survive their predicament, Sonic and co. dealt enough damage to the Egg Piston mk.II to make it go haywire. Despite the increased dangerousness of their situation though, Sonic and co. managed to make the Egg Pistons mk.II blow up with Eggman inside it and escape to freedom.
In Sonic Mania, the Egg Pistons mk.II is fought with Sonic, Tails or Knuckles. In Sonic Mania Plus, it is fought with Sonic, Tails, Knuckles, Mighty or Ray.
Like the original boss in Final Zone, Dr. Eggman uses the Egg Pistons mk.II as crushers. During the initial phase of the battle, Eggman will attack the player with two pistons at time, which will emerge from either the ceiling or floor; Eggman himself hides inside one of these pistons. To damage this boss, the player must attack the piston Eggman is residing it. In addition, after the launch of each pair of pistons, the red bulb on the right will create four damage-inducing energy orbs that fall down slowly while homing in on the playable character. As long as the player is quick and does not leave themselves cornered, these orbs are easily dodged with a jump or Spin Dash.
After landing four hits on the pistons, the Egg Pistons mk.II machine starts to blow up and go haywire, causing the screen to flash red and destroy the bulb producing the energy orbs. After that, the pistons begin deploying individually in quick succession. Before a piston fires itself though, it indicates this by shaking. The order in which the pistons fire is random. However, the player must still attack Eggman, who will now appear in every fourth piston, to damage this boss.
Landing another four hits destroys the Egg Pistons mk.II machine completely and ends the fight. The player can then proceed to the Goal Plate and finish the Act.
The Egg Pistons mk.II is based on the final boss of the original Sonic the Hedgehog, with the main physical difference is that the Egg Pistons mk.II have five pistons while the original only has four.
As of Version 1.04/RC 1.05.0713, when the player enters the room containing the boss, there is a scripted event which automates the player's character's movement to prevent them from being crushed by the entrance/exit pistons that close up.
↑While not listed in any instruction manuals, the internal files in the PC release of Sonic Mania refers to this boss as "EggPistonsMKII".