Nightmare Phenomenon

Nightmare Phenomenon is a phenomena caused by the Nightmares created by Gate in Mega Man X6, that affect Reploids' DNA data and even the environment. Gate was able to create this by analyzing a piece of Zero's DNA, found by him in the remains of Eurasia.

The Nightmare Virus is a specialized enemy that looks different from nearly every other enemy in Mega Man X6. The player gains Nightmare Souls (A bluish orb) by defeating the Nightmares. Also, they'll infect and take control of Rescuable Reploids if given the chance, turning them into Mavericks.

There are also two Nightmare bosses: One Nightmare similar to Zero called the Zero Nightmare, and two giant Nightmare masses that are the first boss of the final stages called Nightmare Mother.

Nightmare Souls
Whenever the player defeats a Nightmare Virus in a level or defeats the Maverick at the end of a level (Nightmares yield a blue Soul, worth 8 points, and Maverick bosses yield a green Soul, worth 200 points,) they will receive a Nightmare Soul. The number of Nightmare Souls collected determines the Maverick Hunter rank of the character that took it and how many parts can be equipped by that character. After defeating the Zero Nightmare and High Max (Or simply waiting; if you wait to a certain point in the game without beating the Zero Nightmare or High Max, they disappear), Dynamo will appear and challenge the player to a fight if they enter a hidden zone. Hitting Dynamo with his weakness (Rain Turtloid's ability) will cause him to drop a green Nightmare Soul; this can be done up to four times per battle.

Nightmare Virus
The Nightmare Virus (ナイトメア・ウィルス) is a enemy found in almost every stage. They can attack the player by shooting at them, or getting close and touching them. They leave Nightmare Souls when destroyed. If the player doesn't take the Nightmare Soul before it vanishes, the Nightmare Virus will reappear, but only one time and it will not leave a Nightmare Soul when destroyed again.

When it is in the same screen of a Reploid in need of help, it will try to turn them into a Maverick. If the Nightmare Virus is not destroyed or the Reploid is not rescued before the Nightmare Virus gets close to the Reploid, the Reploid will turn into a Maverick and attack the player. If a Reploid with a item is turned into a Maverick, the item will be lost forever.

Zero Nightmare
The Zero Nightmare is an off-colored (Pink armor with teal-ish eyes and purple hair) Nightmare similar to Zero. He is the first boss of the hidden areas. When he is defeated, Zero will become playable. He is weak to the Z-Saber.

Nightmare Mother
The Nightmare Mother (ナイトメアマザー) is the boss of the first part of Gate's Lab, two giant masses of Nightmare DNA that spin through the room, stopping every so often to open its "eyes" to attack. Its weak point are its mechanical eyes.

Other enemies and effects

 * Nightmare Bug: A flying enemy in Commander Yammark's stage.
 * Nightmare Cube: A obstacle that appears in the stages of Metal Shark Player and Shield Sheldon.
 * Nightmare Fire: Fire balls that appears in Blizzard Wolfang's stage.
 * Nightmare Insect: (ナイトメア・インセクト) A mantis enemy in Commander Yammark's stage. If you destroy them with any weapon other than the Yammar Option, you will have a quick chance to get by before they regenerate.
 * Nightmare Iron: The iron plates that appears in some stages.
 * Nightmare Laser: Lasers in Shield Sheldon's stage.
 * Nightmare Mirror: A shadowy form of X or Zero that sometimes appears in Rainy Turtloid's stage. It will have the form of Zero if the player is using X, and the form of X with Zero.
 * Nightmare Pressure: (ナイトメア・プレッシャー) The sub-boss of Metal Shark Player's stage. Presumably, it is the core of the trash compactor that antagonises you throughout the stage.
 * Nightmare Random: Round and square rocks that appears in Ground Scaravich's stage.
 * Nightmare Snake: (ナイトメア・スネーク) The five sub-bosses in Blaze Heatnix's stage. They look more like large red rings rather than snakes.