Ultraman Mebius Gaiden: Ghost Rebirth (ウルトラマンメビウス外伝 ゴーストリバース Urutoraman Mebiusu Gaiden: Gōsuto Ribāsu) is a two-part Gaiden by Tsuburaya Productions produced in 2009. It is a prequel to Mega Monster Battle: Ultra Galaxy Legends The Movie and a direct sequel to Ultra Galaxy Mega Monster Battle: Never Ending Odyssey, expands the concept of the Monster Graveyard, and also gives the first look at Nebula M78.
Stage 1: Graveyard of Darkness
Ultraman Hikari sends an Ultra Sign to the Ultra Brothers from the monster graveyard so they decide to investigate. Ultraman Ace and Ultraman Taro start to head there, while Ultraman Mebius, who was patrolling the area nearby, gets ambushed by Grozam. He almost defeats him, but an Inpelaizer intervenes. He struggles to defeat him, whilst Grozam heads to the monster graveyard.
Meanwhile, Ace and Taro arrive at the Monster Graveyard to find that the Dark Four Heavenly Kings, who have been revived are planning to get the Giga Battlenizer from the Valley of Fire in order to use a capsule that contains the hatred of Alien Empera to ressurect him. After a fierce battle, they reveal that they have captured Ultraman Hikari as a hostage. Taro and Ace give in knowing that if they don't they will continue to hurt Hikari.
Mebius defeats the Inpelaizer but another appears and knocks him to the ground. Mechazam then appears and destroys it, curious about Mebius's source of power. He attacks and threatens him, saying that they aren't friends. Mebius arrives at the Monster Graveyard to find Taro and Ace both captured. Alien Mefilas demands that he go into the Valley of Fire to get the Giga Battlenizer. Ultraman Hikari appears too, saying that he needs the Giga Battlenizer to pursue more power. Mebius, heart-broken, heads into Valley of Fire to save Taro and Ace.
Mechazam joins him, still curious about the source of his power. Inside they find a bridge that leads to the Giga Battlenizer, protected by a seal and guarded by EX Zetton. Together, they battle him but he proves to be an extremely powerful enemy, destroying part of the bridge causing Mechazam to fall into the flames at the bottom and be severely injured, but before EX Zetton can continue his attack, Mebius jumps in-between the attack and takes the hit for him.
Stage 2: Resurrection of the Emperor
Together, Ultraman Mebius and Mechazam eventually break the seal and destroy EX Zetton. As they are leaving, however, lava flows from the top of the valley where it was damaged from Mechazam being knocked into it. Mechazam pushes Mebius out of the way and gets hit himself and finally understanding what true power was, protecting comrades, he dies.
Mebius brings the Giga Battlenizer to the Dark Four Heavenly Kings who take it from him and laugh, knowing that they were never going to release Ultraman Taro and Ultraman Ace from the start. Ultraman Hikari suddenly steals it from them however, and with Mebius, frees Taro and Ace. The Dark Four Heavenly Kings are shocked to find that Hikari was tricking them and that Mebius knew that Hikari would never betray him. After another battle, Deathrem and Mebius Killer are defeated, but during the battle Mefilas uses manages to get hold of the Giga Battlenizer and by killing Grozam as a distraction, he inserts the capsule into the Giga Battlenizer. He uses it to locate the new body for Alien Empera, which turns out to be Mechazam. This is revealed to be the reason why Mechazam was created, to be the new Alien Empera, called Ghost Rebirth. All that he needs is for the Giga Battlenizer to be inserted into his chest, but before he can do so the Ultramen try to stop him. Taro, Ace and Hikari struggle to fight back.
Mebius grabs the Giga Battlenizer right as Mechazam is about to take it and tries to convince Mechazam to change back. It almost works when Mebius points out the wound that he has from saving him, but still Mechazam continues to fight Mebius for the weapon. Mebius injures Mechazam on the head, in the same place that he did when they first met. Mechazam cuts Mebius with his sword and light escapes his body and eventually enters the wound and Mechazam remembers who he was, but it is too late. He continues to transform into Ghost Rebirth and asks Mebius to destroy him, while he is still himself. Mebius uses Burning Mebium Dynamite and in a huge explosion, Mechazam dies once again.
After the credits, the Giga Battlenizer is shown floating through space, but is suddenly grabbed by a hand, without the full body being shown. In Mega Monster Battle: Ultra Galaxy Legends The Movie, this is shown to be Alien Zarab, who uses it to re-awaken Ultraman Belial from his prison.
- Mechazam/Alien Empera
- Armored Mefilas
- Mebius Killer/Yapool
- EX Zetton
- Alien Zarab
- Neronga (Ghost)
- Red King (Ghost)
- Woo (Ghost)
- Arstron (Ghost)
- Kelbim (Ghost)
- Ultraman Mebius (ウルトラマンメビウス Urutoraman Mebiusu): Shunji Igarashi (五十嵐 隼士 Igarashi Shunji)
- Ultraman Hikari (ウルトラマンヒカリ Urutoraman Hikari): Keiichi Nanba (難波圭一 Nanba Keiichi)
- Ultraman Ace (ウルトラマンエース Urutoraman Ēsu): Takeshi Kusao (草尾 毅 Kusao Takeshi)
- Ultraman Taro (ウルトラマンタロウ Urutoraman Tarō): Hiroya Ishimaru (石丸 博也 Ishimaru Hiroya)
- Armored Mefilas (アーマードメフィラス Āmādo Mefirasu): Seizo Kato (加藤 精三 Katō Seizō)
- Glozam (グローザム Gurōzamu): Hisao Egawa (江川 央生 Egawa Hisao)
- Deathrem (デスレム Desuremu): Daisuke Gori (郷里 大輔 Gōri Daisuke)
- Mebius Killer (メビウスキラー Mebiusu Kirā): Ryoichi Tanaka (田中 亮一 Tanaka Ryōichi)
- Mechazam (メカザム Mekazamu): Hideyuki Hori (堀 秀行 Hori Hideyuki)
- Zoffy (ゾフィー Zofī)/Narrator: Hideyuki Tanaka (田中 秀幸 Tanaka Hideyuki)
- Ultraman Jack (ウルトラマンジャック Urutoraman Jakku): Jiro Dan (団 時郎 Dan Jirō)
- Ultraseven (ウルトラセブン Urutorasebun): Kohji Moritsugu (森次 晃嗣 Moritsugu Kōji)
- Ultraman (ウルトラマン Urutoraman): Susumu Kurobe (黒部 進 Kurobe Susumu)