Nightmare Mother

Nightmare Mother (ナイトメアマザー) is the boss of the first part of Gate's Secret Lab in Mega Man X6. Each Nightmare Mother is an aggregation of Nightmare Viruses that spin throughout the room, stopping every so often to open their eyeball-shaped cores to attack.

Strategy
The Nightmare Mother moves around the room in a circular pattern, each one always on opposite sides, starting on the top left and bottom right of the room. They stop for a brief moment between each move, and they may change their direction. After losing half of their life energy, and on higher difficulty levels, there is no interval between the moves. The speed of the transition between walls also depends on the difficulty level, and on harder difficulties they will occassionally shot energy spheres while moving. Every once in a while, they will stop to launch an attack from their cores. Occasionally, they will stop stacked on the same surface. When one of the two cores are destroyed, the empty shell of DNA will slam into the surfaces while the other one launches attacks, further limiting the space the player has to maneuver.

Their only vulnerable area are their cores, which are weak to the Metal Anchor (with X) or Rakukoujin (with Zero). They are usually protected by the DNA-shaped mass, but are vulnerable while attacking. X with the Shadow Armor can deal massive damage to the cores just by unleashing his Charge Shot or the Giga Attack on it while it is exposed.

The attack each core can use is:


 * Water - The most common attack, used from any direction. The core shots a water projectile similar to the Goo Shaver from Mega Man X5 that travels down walls and across floors.


 * Thunder - Only used when the Nightmare Mother is on the ceiling. The core faces down and fires blue energy balls from overhead that fly across the screen and strike the floor with thunderbolts, and smaller energy balls that bounce off walls.


 * Flame & Fireball - The effect depends on the core's possition. If the core faces down, it shoots a fireball at the floor, causing it to erupt in flames, forcing the player to Wall Kick to avoid it. If the core faces up, it releases several fireballs, which can be avoided by staying close to the Nightmare Mother.

They have a total of five possible combinations: Water + Water, Thunder + Thunder, Water + Thunder, Water + Flame & Fireball, and Thunder + Flame & Fireball. The Flame & Fireball attack will not be used by the cores at the same time.

Other appearances
Nightmare Mother appeared as an unit card in TEPPEN.

Trivia

 * The way that they can only be damaged while attacking is very similar to the Devil series of robots (e.g., the Yellow Devil) from the original Mega Man series.
 * The Nightmare Mother shares its boss theme with D-1000.