Egg Reverie Zone

The Egg Reverie Zone is the thirteenth and true final Zone in Sonic Mania. It is only accessible over the course of the game to Sonic the Hedgehog upon collecting all seven Chaos Emeralds. Alternatively, the player can use the Level Select to access this Zone with Miles "Tails" Prower or Knuckles the Echidna.

A void where time and space seemingly does not exist, the Egg Reverie Zone displays the final conflict between Dr. Eggman and the Hard Boiled Heavies' leader, the Heavy King - who has transformed into the Phantom King, for possession of the Phantom Ruby, all while Super Sonic attempts to subdue the two and take the gemstone away from the power hungry monarchs.

Overview
The Egg Reverie Zone is a purple-hued void of a barren wasteland where time and space act erratically. A single platform exists within the Zone, with several stage lights brightening up the platform.

Story
After obtaining all seven Chaos Emeralds, Sonic the Hedgehog was transported to the Egg Reverie Zone by the Phantom Ruby after defeating Dr. Eggman inside the Titanic Monarch Zone. Within this dimension, a modified Heavy King, now known as the Phantom King, takes the Phantom Ruby floating in front of Sonic, shortly before Eggman in his Kleptomobile arrives in an attempt to take the ruby back. Sonic, however, transforms into Super Sonic and fought off both the Heavy King and Eggman.

After Eggman and Phantom King are defeated, the Phantom Ruby and the Chaos Emeralds interact with one another briefly. Sonic (now back to normal) and the Phantom Ruby are then taken through a wormhole created by the ruby while the Titanic Monarch crumbles due to the wormhole.

Gameplay
The Egg Reverie Zone is essentially an empty arena with no gimmicks or objects. The usual time limit is also meaningless in this Zone, as the Zone timer erratically jumps between random values, indicating the fluctuating space-time in this Zone. To sustain the player's Super State which is needed for this Zone, Rings are floating around in an aimless pattern for the player to pick up. Moving close to the Rings will pull them to the character, similar to the Thunder Shield. When the playable character is airborne, he is capable of performing a dashing attack by pressing the jump button. Doing so will consume five Rings.

Bosses
Being the true final boss of Sonic Mania, the Egg Reverie Zone casts not one, but two bosses to fight: the Kleptomobile and the Phantom King. However, in this zone, Sonic automatically uses the seven Chaos Emeralds to become Super Sonic. The Rings in the Zone can be used to refill the player's Ring count, which needs to be kept with at least one Ring in order to keep the hero's Super State: if the player's Ring count hits zero, the fight will end, and the player will lose a life.

The fight is tricky at first glance, but it can be a relatively easy finale for a seasoned player. The player begin by facing the Phantom King; once the player hit the Phantom King or if enough time passes without the player making a move, it will switch to the Kleptomobile phase. Hitting one of the bosses will result in the other boss showing up. In terms of attack patterns, the Phantom King uses energy spheres, which are either used to form a nearly impenetrable shield around this boss or as projectiles that can take away ten Rings from the player if they hit. The Kleptomobile on the other hand attacks with rapid punches that can repel the player or a powerful beam.

To defeat these bosses, the player must hit each of them eight times.

Trivia

 * A "reverie" is the idea of a daydream or being lost in one's thoughts, which fits the description of the Zone.
 * Adding a Goal Plate via Debug Mode will cause the player to instantly lose a life once it is flipped.
 * Whilst normally, this zone can only be accessed by Sonic, it can also be accessed by Knuckles when "& Knuckles" mode is activated. The ending shows a still image of Knuckles reading a book called "Sonic Mania & Knuckles" to a group of excited animals, as Sonic and Tails look in confusion. This special ending plays a track heard nowhere else in the game; a remixed version of the title screen music from Knuckles' Chaotix.
 * This Zone is not added to the stage select available from a cleared save file, even when completed. The only way to access this Zone under normal circumstances is to arrive to it by completing Titanic Monarch. It can, however, be played directly by using the stage select cheat code.
 * On the secret stage select menu, Egg Reverie Zone is represented by an icon of the Death Egg. The icon itself is originally from the Sonic the Hedgehog 2 stage select menu.