Nightmare Phenomenon

The 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. If the Nightmare Soul they leave when destroyed has not being collected by the player after a few seconds, the Nightmare Virus will reappear. Destroying them a second time will not yield a Soul orb.

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 they will receive a Nightmare Soul (Nightmares yield a blue Soul, worth 8 points, and Maverick bosses yield a green Soul, worth 200 points). 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 by simply waiting: if the player gets to a certain point of 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 (Rainy Turtloid's ability) will cause him to drop a green Nightmare Soul; this can be done up to three times per battle.

Zero Nightmare
The Zero Nightmare is an off-colored (pink armor with teal-ish eyes and purple hair) Nightmare similar to Zero created by Gate through use of Zero's DNA. He is seemingly incomplete, and mentally insane, one moment claiming that X has gone Maverick when he throws in his face that he isn't the real Zero, then the next moment incoherently shouting out "BLUE LIGHT... MUST KILL!", among other phrases. He is the first boss of the hidden areas. His attacks and moves are similar to those of Zero in X5. When he is defeated, Zero will become a playable character. He is weak to the Z-Saber, because he is a nothing but a mere copy of the original Zero; also, this could be a possible reference to Metal Man, as both are weakest against their own signature weapons. The music in his battle is the same music featured during the X vs. Zero fight in X5.

An alternate unlockable color for Zero in Tatsunoko vs. Capcom bears a resemblance to Nightmare Zero, being purple, but with white hair and dark purple arms and legs. It doesn't completely look like it, but could be considered a Nightmare Zero tribute.

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, which are weak to the Metal Anchor.

Nightmare Virus
The Nightmare Virus (ナイトメア・ウィルス) is an enemy found in almost every stage (except the intro level and the first Secret Laboratory level). They can attack the player by shooting at them, or by 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 (which somewhat resembles a zombie version of itself) and attack the player. If a Reploid with an item is turned into a Maverick, the item will be lost forever.

Nightmare Bug
Nightmare Bug is a bug enemy that flies near the player. They can't be destroyed, only driven away. It appears in the stages of Commander Yammark, Shield Sheldon and Blaze Heatnix.

Nightmare Insect
Nightmare Insect (ナイトメア・インセクト) is a mantis enemy that appears in Commander Yammark's stage. If they are destroyed with any weapon other than the Yammar Option they will regenerate, leaving the player a quick chance to get by.

Nightmare Pressure
Nightmare Pressure (ナイトメア・プレッシャー) is the sub-boss of Metal Shark Player's stage. Presumably, it is the core of the trash compactor that antagonises the player throughout the whole stage. The compactor (but not the Boss) returns in Gate's stage if the player chooses Zero.

Nightmare Snake
Nightmare Snake (ナイトメア・スネーク) is the name of the five red Mechaniloid sub-bosses in Blaze Heatnix's stage. They look more like large red rings rather than snakes, though. They can only be defeated by destroying the four green cores around their frame. They are weak to the weapon gained from Infinity Mijinion, Ray Arrow, and X's Nova Strike (his Utlimate Armor's Giga Attack).

Hazards and other effects

 * Nightmare Cube: An obstacle that appears in the stages of Metal Shark Player and Shield Sheldon. The red and brown ones can be destroyed with weapons gained from Ground Scaravich, while the rest can only be pushed by these same attacks.
 * Nightmare Dark: A portion of the screen will be black, and visible/semi-visible portions will be moving in a pattern that greatly reduces visibility, increasing the difficulty of clearing by a sizeable percent. This phenomenon happens in the stages of Commander Yammark and Rainy Turtloid.
 * Nightmare Fire: Falling fire balls that appear in Blizzard Wolfang's and Infinity Mijinion's stages.
 * Nightmare Iron: Iron plates that appear in the stages of Blaze Heatnix, Ground Scaravich and Infinity Mijinion.
 * Nightmare Laser: Lasers in Shield Sheldon's stage. They're needed to complete the puzzles there.
 * Nightmare Mirror: A shadowy form of X or Zero that sometimes appears in Rainy Turtloid's and Blizzard Wolfang's stages. It will have the form of Zero if the player is using X, and the form of X with Zero. They are similar to the Zero Viruses from X5.
 * Nightmare Rain: The Acid rain in Rainy Turtloid's stage and Gate's stage if you chose X. It slowly drains the player's lifebar.
 * Nightmare Random: Round and square rocks that appear in Ground Scaravich's stage and the 2nd of the final stages (where the player has to fight through two consecutive stages without resting).