Nightmare

Nightmare is a wicked final boss character in the Kirby series. He only appears in two games, Kirby's Adventure and its remake. Nightmare is responsible for corrupting the Fountain of Dreams and attempting to spread his nightmares all across Dream Land. King Dedede tries to stop Nightmare from succeeding by breaking the Star Rod, but Kirby unwittingly summons Nightmare, and thus has to defeat Nightmare before his evil plans become reality.

Nightmare's affiliation and relationship with Dark Matter is currently unknown, and has never been touched upon in the series.

Nightmare is also the main antagonist of Kirby: Right Back at Ya!, where he acts behind the scenes as his company, Nightmare Enterprises, tries to take over Pop Star.

Physical Appearance
Nightmare begins the fight in his Power Orb form. In this form, Nightmare is a dark sphere covered in silver, glowing stars. A gradient runs across the sphere: the top of the sphere is dark blue while the bottom is dark pink. This design remains the same between both the original game, Kirby's Adventure, and it's remake.

After Kirby defeats him in his orb form, Nightmare reveals his true form. In this form, Nightmare resembles a wizard wearing a spinning, tornado-like robe. In the official art for Kirby's Adventure and the anime his robe is covered in stars, just like in his first form. In the actual games, Nightmare's cloak is simply a dark purple shadow-like robe. Underneath his cloak is his weak spot, a tornado-like accumulation of darkness. In the original game, Nightmare has two silver shoulder pads, and a small red medallion around his neck (obscured by his chin in-game). In the games Nightmare has human-like teeth, while in the anime his teeth are sharp and jagged. He has two thin, bony arms.

In Kirby: Nightmare in Dream Land, Nightmare's second form is slightly changed. He now has a total of four shoulder pads instead of two, and much longer horns on his helmet. His chain and medallion are now both visible during the fight. He is also almost as tall as the screen now.

Kirby's Adventure and Kirby Nightmare in Dream Land
Nightmare is a powerful entity that serves at the final boss in both Kirby's Adventure and its remake. In both games, he can only be defeated by the powerful Star Rod that Kirby collects in both games.

In Kirby's Adventure, Nightmare takes control of the Fountain of Dreams in an attempt to extend his control over Dream Land. Trying to prevent this, Dedede breaks the Star Rod and scatters it around Dream Land, temporarily leaving Nightmare unable to take control and seems to trap him inside the Fountain of Dreams. Kirby, unaware of Dedede's intentions, restores the Star Rod and places it back in the fountain. With the Star Rod back in place, Nightmare reveals himself. Nightmare and Kirby then fly into space (Kirby did this with the help of Dedede).

In his initial form Nightmare, for the most part, stays on the right side of the screen, shooting stars at Kirby. The entire battle takes place in space as the two are falling to some floor (presumably Pop Star's surface). As such, if Kirby doesn't deplete Nightmare's health bar in time, Nightmare will flee, and Kirby will crash into the ground and lose a life. After the final blow is struck, Nightmare retreats and flies to Pop Star's moon. Kirby follows him using a Warpstar.

In his second form Nightmare attacks Kirby by shooting stars at him, ramming into him, and using his tornado-like core to drill into him. He takes fewer hits to defeat than in his first form, but can only damaged by hitting his weak spot, the accumulation of darkness at his core, is usually protected by his impenetrable cloak. He reveals his weak spot whenever he attacks Kirby. After Kirby lands the finishing blow, Nightmare's body explodes, destroying a huge portion of the moon as a result. After this, Kirby returns to the Fountain of Dreams, places the Star Rod back in there, and everything returns back to normal.

Kirby Canvas Curse
In Kirby Canvas Curse, Nightmare appears as a painting in Paint Panic. He is the hardest painting to draw with four stages.

In the Anime
Likely because the Kirby anime was meant coincide with the release of Nightmare in Dream Land, Nightmare is the main villain in Kirby's anime series, despite actually appearing in only nine episodes (the whole series had 100). In a contrast to his fairly nonthreatening goal of simply spreading bad dreams in the game, Nightmare's goal is to conquer the universe. He's responsible for the creation of Nightmare Enterprises (known as Holy NightMare Co. in Japan) He creates and sells hordes of monsters that Kirby often has to fight. It's implied that the monsters eventually turn on the customers as well. The money he makes from it always goes to his conquest goals. There was a time when the Star Warriors and Galaxy Soldier Army stood in his way, but his army of monsters wiped them all out except Meta Knight, Kit Cosmos, Sir Arthur, Sir Falspar, Sir Dragato, and Sir Noisurat.

It's mentioned by Kabu that Nightmare created one monster that didn't obey him, though who it isn't ever stated. This is heavily implied to be Kirby, but it's possible that it might also be Meta Knight, as Kirby wasn't even born yet while the great war was going on.

Besides being able to create powerful monsters, Nightmare is also able to manipulate other peoples' minds, and even brainwash them. Like in the games, he is also impossible to hurt without the use of the Star Rod. Nightmare resides deep within his fortress, the Destrayer, for the majority of the show, creating monsters.

Nightmare rarely interacts with anyone and spends his time alone. Occasionally Nightmare speaks to Customer Service concerning their business, but mainly exists as a figurehead of the company.

Throughout the series, Nightmare is seen simply watching Kirby and Dream Land, and never seems to take Kirby for a threat. He constantly watches Kirby fight his monsters that he sells to King Dedede. One of the few notable actions was when he sped up the rate of an asteroid that was heading for Dreamland, which he seemed to mostly just do for his own amusement, as well putting money in his pockets from his best customer: (and "sucker") King Dedede.

Towards the finale Nightmare seems to decide to end his amusement with Kirby and sends some of his Destrayer ships to kill him, but this also fails. Nightmare responds by sending another six, but these are destroyed by Meta Knight's battleship the Halberd. Even when the Halberd heads towards the Destrayer, Nightmare still doesn't take the one ship for a threat and attempts to stop with one last monster called Heavy Lobster.Even though that monster failed, it proved nothing compared the defenses of the Destrayer, which the Halberd only just barely managed get past with help from the other Galaxy Soldiers and Star Warrior who each hijacked a Destroya. Despite that, once the Halberd entered and confronted Nightmare, it proved unable to do a thing against him and his fortress' defenses soon nearly crippled the ship. During this time Nightmare appears as a giant dwarfing the Halberd, though considering this form didn't do anything it's likely it wasn't real. Nightmare then kidnapped Tiff (Fumu) to lure Kirby into a fight with him. As Fire Kirby, Kirby tried to attack him but his fire breath had no effect. Nightmare then entered Kirby's mind to torture him before finishing him off, but Tiff, who was also in there, tossed Kirby a dream version of the Warp Star to Kirby, which he swallowed to gain the Star Rod ability- the one thing that could damage Nightmare. Kirby harnessed the power of the Star Rod and used it to destroy Nightmare.

Nightmare was also the real villain in Kirby of the Stars Pilot and the one who sends all the monsters at Kirby. In the end he is seen attacking Kirby and his friends with some kind of energy beam before Kirby wakes up and realizes that it was actually a nightmare.

Kirby: Right Back at Ya!

 * "Sell him Fofa. Better yet, chop it and charge him double!" *laughs* -Nightmare to Customer Service, The Fofa Factor
 * "Well, I don't know about you, but I'm growing rather impatient. What do you say we speed it up a bit?" -Customer Service to Nightmare, Prediction Predicament - Part I
 * "What a wonderful idea!" *laughs* -Nightmare, Prediction Predicament - Part I
 * "Well, it looks like Kirby and his Warp Star aren't invincible after all." -Customer Service to Nightmare, Air-Ride-in-Style - Part II
 * "It's only a matter of time until the Warp Star will be ours for the taking." *laughs* -Nightmare, Air-Ride-in-Style - Part II
 * "They're growing desperate... They'll realize I have them beaten. I was hoping they'd be foolish enough to attack, so I've prepared a surprise for them." -Nightmare about the Halberd crew, Combat Kirby
 * "Heh. It was a mistake to come here, Kirby. As you can see, you and your puny band of Star Warriors pose no threat to me. Challenging me is the last mistake you will ever make!" -Nightmare, Combat Kirby
 * "Hahaha... It's too late, child. Kirby is about to face his worst nightmare." -Nightmare, Fright to the Finish
 * "Hahahaha... This is checkmate, Kirby. The game is up!" -Nightmare, Fright to the Finish
 * "We shall see about that! Before this match is over, you will learn the force of my power." *laughs* -Nightmare, Fright to the Finish
 * "Hahahaha... Your friend has chosen an unfortunate time for a nap!" -Nightmare, Fright to the Finish
 * "He has used up all his energy... Kirby is now completely helpless. I can crush him with little effort... But first, some fun! I shall enter his sleep and give him a nightmare, and you can join him. We think you'll find this dream a real scream!" -Nightmare, Fright to the Finish
 * "Ahahahahaha! What a dreamscape. All Kirby cares about is food!" -Nightmare, Fright to the Finish
 * "You're wasting your time! This is Kirby's dream. There is no Warp Star here!" *laughs* -Nightmare, Fright to the Finish
 * "Foolish child... There is nothing you can do to help your friend." -Nightmare, Fright to the Finish
 * "He swallowed the Warp Star..." -Nightmare, Fright to the Finish
 * "The Star Rod?! AAAAH!" -Nightmare, Fright to the Finish
 * "Aah! Aaaah! No... How did Kirby discover the secret?! That pitiful little Star Warrior has found my only weakness! I am helpless against the power of the Star Rod!" -Nightmare, Fright to the Finish
 * "True to my name, I am but a dream that lives in your heart. Therefore, I am immortal. For as long as there is fear in your heart, I will someday return." -Nightmare's last words, Fright to the Finish

Trivia

 * In the Japanese version of the anime's last episode, Nightmare says these famous lines while Tiff and Kirby and the others are escaping his fortress: "True to my name, I am but a dream that lives in your heart. Therefore, I am immortal. For as long as there is fear in your heart, I will someday return." These lines were edited out of the dub. It is also interesting to note that these lines could also be a reference to the fact that Dracula of Castlevania fame is often resurrected many times thanks to the darkness in the hearts of people who wish to see his revival and pay him tribute.
 * Despite only making one appearance in a game, Nightmare is a memorable villain. He has three cameos, one in Kirby Squeak Squad as an unlockable picture of Kirby antagonists, another in Kirby: Canvas Curse as a picture Paint Roller conjures, and finally in Kirby Super Star Ultra as a card in Kirby Card Swipe. His appearance in the last is the same as in Kirby: Nightmare in Dream Land, whereas the first is a closeup that seems to combine features from both appearances. His orb also made a brief appearance in the spinoff, Kirby's Avalanche.
 * Marx later reused the same arena - the moon. In Kirby Super Star and Kirby Super Star Ultra, the moon's surface looks similar to its original appearance in Kirby's Adventure. Kirby: Nightmare in Dream Land is its only oddball appearance - if you went by the remakes, you'd have no idea that Marx's battle took place on the moon!