Abyss is a legendary creature, forgotten by time and believed to be just a fairy tale. A forbidden weapon with the powers of a god, Abyss was created in ancient times during an era when magic prospered, and sealed off in an underground temple where it spent untold centuries in a deep sleep. But when its resting place was disturbed by the actions of a "pirate organization" seeking to claim it, Abyss awoke and his unparallel power began to stir the world. Its awakening sends forth hideous waves which mutates all life on the seas, while the accursed winds blowing from the seas scrape the lands and kills off any kind of life (animals and plants alike) on its path. Abyss is something akin to entropy incarnate, a fabled monstrosity whose ultimate goal is to bring the world back to primordial times, devouring all life on the planet to return it to the "Sea of Genesis" (はじまりの海 Hajimari no Umi ), the primordial sea from where all life came from.
With Abyss now awakened the countdown to destruction has begun. Having been involved in the actions that caused its rise, Ruby Heart sees herself involved in this crisis and determined to gather heroes from both universes in order to stop it.
Abyss is faced in three different forms or stages. Abyss' true form or core is a large, black sphere with green lines of magic symbols surrounding it, and it is capable of creating bodies with the use of a green liquid substance it controls at will.
First Form - Armor of Erosion
The first form faced is a large suit of black armor known as the Armor of Erosion (波蝕の鎧 Hashoku no Yoroi ). This armor was built by Abyss' creators in order to control its enormous powers. Abyss is forced to use it due to being in an incomplete form, materializing it around its core and filling it with the substance in order to control it, jutting two large green horns out of the top of the mask. Although the armor was created specifically to restrict its power, Abyss is still able to exert an incredible amount of strength from within it.
The first battle takes place inside a large underground temple, which according to the ending appears to be located inside a volcano in the middle of a vast body of water. The Armor of Erosion is slow-moving but possess powerful attacks, including a dash attack, a palm strike, a large beam and the ability to generate spears out of the green substance inside it. This form has Hyper Armor, which means its moves can't be interrumpted and must be avoided or jumped over in time.
Second Form - The Guardian
The second form is a humanoid-shaped being made up of the green substance, known as the Guardian (守護者 Shugo-sha ). A transitory form, the Guardian is created as a defense after Abyss is freed from the constrains of the armor, retreating as the process to attain its complete form begins. This form is actually just a separate fragment of Abyss' entire being.
Following the first form's defeat, the armor is absorbed into the floor and the temple crumbles and sinks slightly into it, as its now entirely covered in green substance. The Guardian is capable of turning its hand into a powerful cannon capable of shooting fire blasts and energy beams, as well as sinking into the floor and creating large paralyzing bubbles.
Final Form - Abyss
The complete form assumed by Abyss after restoring its full powers. Abyss appears as a large beast-like demonic creature made up of the same substance it uses, now turned blood red in color. Abyss holds godlike powers in this form, seeking to fulfill its ultimate goal: to devour all of existence and return it to the Sea of Genesis. In this form its core finally becomes vulnerable to attack, as Abyss leaves it vulnerable every time it attacks.
Once the Guardian is defeated, it sinks into the ground as the temple is fully absorbed, the green liquid turns red and the massive Abyss rises from beneath. The final form attacks with sheer brute strength, striking the ground with its tentacle-like limbs or jumping across the stage like a shark, and powerful attacks using its liquid in the form of rising pillars or flying claws.
Once this form is defeated, Abyss' core seems to lose its powers as the symbols around it vanish and then it releases an explosive shockwave. Later seen in the ending, the orb appears cracked and powerless in Ruby Heart's hand, who contemplates it for a moment before tossing it over her shoulder and into the oceans below.
- Abyss is the first fully original boss character created for the Marvel vs. Capcom series, and the 2nd of 3 original boss characters following Cyber-Akuma and Ultron Sigma, both hybrid Marvel/Capcom characters.
- Official concept art for Marvel vs. Capcom 2 writes the name of Abyss' armor form literally as "Wave Touch Armor" (波触の鎧 Namizoku no Yoroi ), while later sources uses "Wave Erosion Armor" (波蝕の鎧 Hashoku no Yoroi ) instead. As the official translation of the term is "Armor of Erosion", the latter is presumed to be the correct term.
- His 3rd Final Form looks similar to Marvel's symbiotes due to have sharp teeths, long tongue and drooling like Venom.
- Marvel vs. Capcom 2 Graphic Arts, concept art featured in Monthly Arcadia Vol.3 (March 30, 2000)
- Marvel vs. Capcom 2, "The Approaching Mystery of the Last Boss!!". From Monthly Arcadia #7 (May 30, 2000), Page 30.
- Marvel vs. Capcom 2, "Capcom Side New Character: Ruby Heart". From Dreamcast Magazine #57 (February 4, 2000), Page 174.