Nightmares initially appear on the enemies' side of the field in the form of a small whirlwind (they cannot be damaged in this form). After a few seconds however, they will start moving around MegaMan's side of the field, attacking him with a Wide Sword-style attack after three moves; sometimes they will attack MegaMan from behind. Furthermore, Nightmares are immune to everything except Sword-type attacks and Battle Chips or Anti Damage, and are unaffected by holes and panel effects. Because they appear on MegaMan's side of the field, Battle Chips like the MoonBlade are effective against Nightmares.
Nightmare is a purple variant with red markings.
Blackmare (ブラックメア,Blackmare) is a blue variant with red marikings.
Darkmare (ダークメア,Darkmare) is a red variant with green markings.
NightmareSP (ナイトメアＳＰ,NightmareSP) is a black variant with yellow markings.
RareNightmare (ナイトレア,RareNightmare "Nightrare") is a green variant with light purple markings.
RareNightmare2 is a yellow variant with white markings.
Deleted Nightmares yield the Summon Black (サモンブラック,Samon Burakku) series of Battle Chips. These chips summon a Nightmare virus from any hole on MegaMan's side of the field, which attacks the nearest enemy with a Wide Sword type attack. These chips are non-elemental.