Mercer was first a brood of the Blacklight virus unleashed in New York City. This particular sample of the virus was kept in a vial within a secret lab underneath a house in a Culdesac. Danno-048, in Spartan-II form, stumbled upon the lab and accidentally knocked the vial over, where it crashed on the ground. Since everyone else around him was busy fighting zombies, they were oblivious to it, as the Virus consumed Danno's body... Danno's Shadow-spirit was then in an inactive state as it left the area.This virus, which eventually grew a body out of lots of microscopic Biomass, and after consuming the Queen of Alien King's Hive to grow, dubbed itself "Mercer", after the character in the Prototype series, whose image it copied as it grew. It then attempted to gain allies as it's powers began to develop, growing stronger by the minute. It eventually went to Manhattan, now 'NYZ', to set up a base of operations. After a few cities around the world, including Los Angelas, was nuked to stop the zombie spread which spawned from the virus, Mercer laid low in NYZ in order to preserve his hunting grounds.
Eventually, a Sith fleet under the rule of Darth Malak entered the RP, and Mercer, seeking to increase his power, looked for Marquis's assistance to conquer the Sith fleet and push them back. But Marquis did not know his true intentions: To consume Malak, in order to have control of the Dark side of the Force, and have a whole fleet of Sith to control, conquering worlds and consuming many, many thousands of people on the planets they conquered, Mercer constantly evolving with every person consumed, yet the rest of the Sith were unaware of his true identity, as Mercer was always under the guise of Malak.In the meantime, after 'Malak' left to conquer, the rest of the people in the RP was unaware of where he and his fleet went, until after Earth was covered in a veil of Twilight by Zant. When he came to Earth, 'Malak' was suprised to see it covered in darkness, but moved his fleet in anyway, in order to consume and evolve further. However, the Sith fleet was all but destroyed by Marquis, a couple of other Spartans from ANVIL, Exon-IV, and other smaller groups, and then Malak's own ship, the Leviathan, was borded by the team. He showed impressive skill with both the Dark side and Lightsaber skills, but what Mercer didn't know was that the Dark side was greatly affecting his health, progressively degenerating his body and causing great pain, so the RP group managed to defeat him somewhat easily. After his body was burned and the biomass regenerated back to Mercer form, he lost control of the Dark side, and so his body begin healing. The group now has a shaky alliance with him since he offered them guidance to the Twilight realm. When he happened upon the Twilight realm via a shadow portal while still in Malak form, Mercer consumed one of the Shadow beings there and discovered Midna-Dan being used to serve Zant by watching the Shadow being's memories. Since then, he has assisted the RP group in finding three objects of darkness, which were somehow suppossed to be of help in defeatind Zant, but no one knew how.
When entering the Twilight realm, he assisted in storming the Throne room. He helped to defeat, (But failed to kill) Zant's main shadow guard. Since the group has reentered the "Light" world, Mercer has never been seen since....During the second invasion of the Twilight realm, Mercer was spotted outside the palace, then disappeared before anyone could get a good look at him. He is apparently restarting the viral spread of the Blacklight virus across the United States, and in certain areas across the World. The RP Team of Marquis, Midna, Alien King, Shotgun, and Helenna have gone after him. The group entered the heavily infected NYZ, much more dangerous than the last time they were there, and found from one of Mercer's Evolved pawns where he was. Mercer revealed his true plans for Earth, and stated that The Alien Queen, Alien King's number one priority, was going to be used for breeding something to make human beings incapable of death. He then stated that the only thing keeping him from his goals was the remaining 10 Evolved that were going to fight with him... he consumed them all and became empowered, managing to make an extreme challenge for the RP group, knocking out Danno before they begun.
Marquis, Alien King, and Blair fought against Mercer.... Alien King was nearly killed in the battle, but Mercer made the mistake of focusing most of his attention on Alien King, allowing Marquis to make several lethal attacks; But each time, Mercer continued to regenerate his body. Danno carried with him a serum of The Cure... a chemical designed to exterminate the Blacklight Virus cell by cell... after Mercer's arms were torn off twice, Marquis injected him with it after Mercer quoted, "Huh. Welcome to the top of the food chain." Every cell of Mercer's body was then erased from existence, killing him off once and for all. The Alien Queen was then rescued, Marquis and Alien King escaping separate from the Queen, who was saved by Blair and Danno... the three used a Helicopter to escape the ensuing explosion of a Nuclear device previously set by an anonimous faction. The Queen was saved from Mercer's fate.... and the Blacklight virus was erradicated. Mercer was finally destroyed.Recently, however, in another Dimension, it was discovered that Mercer somehow survived the previous fight.... he seemed to be (Somewhat) restored to his previous power before the second NYZ viral spreading. But he seemed a little different from before.... when he activated his powers, they were a very dark shade of brown, and his blood was thick, dark, and gushed very little. He seemed to be affected by what he was consuming; since the majority of the Biomass in that world was infected by a zombie plague very much like that on Dead Island instead of the cleaner, more efficient Blacklight virus, his body was somewhat downgraded as well. After a brawl with Alien king and Ninja Master, then being chased by Gaara and battling with Marq, his powers seemed a little bit developed, but the mutation was lower in health than before. He considered Gaara a worthy opponent, and after only a few minutes of ssparring with him, he realized that there was something else beneath the shell that was Gaara's body: He could see the demon within. Mercer then split his body into a thousand shards and flew away, as he realized that at his reduced state he was no match for Gaara. Later, when James Heller was introduced, Mercer came out and revealed himself again. Since then, he has been allies with the rp group, much to the dislike of Heller. They worked together to vanquish the release of the Blacklight Virus on the MAKO Colony, Mercer working with Llid (Who took a liking to him). Afterwards, Mercer gave Marquis details on the Third Prototype he accidentally created once in a battle with Cole Mcgrath.
Later, the Third Prototype developed a Scheme that destroyed the Capitol. He then evaded the fire of the Investigating UCR Fleet, and boarded the Hangar, where he and Heller fought. However, even being more powerful than Mercer in the state he was in, James was no match for the Third Prototype's power. He was quickly consumed.
When Heller's Daughter, Maya, was discovered to be in the Hangar, the Third Prototype went to consume her; but Alex came in and stopped him. They then fought as Marquis entered and fought off the Third Prototype's Temporary Partner, Protoman. After The Third Prototype found he couldn't survive on his own, he consumed Protoman; however, this only extended his time of life, as Alex wouldn't give up. When Marquis evacuated the air in the Hangar to create a Vacuum, the Third Prototype and Alex had their final discussion:
Dude: You can't defeat me without sacrificing yourself... you wouldn't do that...
- Alex: I don't care anymore. There's nothing left for me in this world. I am no longer the enemy I was facing Heller. I'm just what I am...
- My name......IS ALEX MERCER!!!!!
" Hello. It's me, Alex... I recorded this prior to me coming into battle... I sensed the third was still alive. I knew he evolved beyond the point of me and James taking him down together... so I decided to do.. what I HAVE to do. I'm going to do what I should have done so many years ago.... I will destroy the Virus. Once and for all.... I cannot live through having the memories..." (The song at 7:40 plays)http://www.youtube.com/watch?v=3dmu0E0p-7w
- "I found the truth.
- Found it.
- Didn't like it.
- Wished the hell I could forget it.
- When I close my eyes, I see the memories of a thousand dead men; Screaming as I take their lives...
- Moments I'll relive forever.
- What have I become?
- Something less than human....
- also something more."
- Later, the Babylon came on board briefly to collect what remained of Mercer; a bit of Black fluid. He teleported out with the vial of the Blacklight virus, supposedly to the storage Planet he has; so that one day, when they need him... Alex Mercer can be called upon once again.