Micah

Funny rat man. Haha, Rat King, except he's an abberation, an affront to god. Merzen Scientists fucked with local wildlife that they made a whole ass rat person.

Merzen is full of all sorts of oddities and strange anomalous things. A good portion are things that just exist, like the crazed monsters out in the wilderness, to strange eldritch cats with too many eyes, to roads that never seem to end. However there is a small subsection of creatures that are artificial in nature. Two that come to mind are [[ZERO]], a Solraine (sun entity) who had his entire being flipped inside out and is now a ghost that violently haunts the planet; and the man of the hour, an antho rat who goes by the name of Micah.
Micah started his life out just like any other critter on Merzen, living a simple life as a simple toxic rat at home in the strange network of corridors and waterways that is the Merzen Sewer system. Avoiding Selines, eating the scraps that find their way down in the grimy sewers, and overall doing what it is that wild rats do. It wouldn't be until he was scooped up by a strange group of Solraine while feasting on a carcass and taken to a strange place. This strange place would not only be the very place he was.... changed at a fundamental level, but also the source of many nightmares to come. The Devil's Lab, a place where the greedy test their unsavory desires upon unwitting test subjects, from the critters they created to the people they scooped off the streets, experimenting and pushing the very bounds of entity and organic life to their brink.
Micah endured endless experimentation during his time there, gradually becoming the thing he is now. The equipment constantly in and out of him, the noise, the screams, all flooding his newly growing mind and becoming more and more aware of everything that is going on. He'd be there for years, his DNA being ripped apart and restructured by those who play god, tormenting him to witness his own body become something different. An abomination, an affront to god himself. Standing as a really wrinkly, patchwork abomination of rat. A sick game to the one who ran it.

After the years of living within those sterilized halls, Micah grew into a nihilistic sort of person. Mean, bitter, and distrusting of anyone he was allowed to talk to. It wouldn't be until he heard the screams of a child in a room nearby that his heart moved an inch on anything. It started as curiosity, as Micah wasn't aware of many other experiments that went on, but upon meeting the young Illiven in the room he crawled through the vents to get to he understood what was going on.
It wasn't out of humanitarianism that Micah decided to help Austin, the child, escape. At least, not at first. It was a mutual goal, and Austin had the firepower to pull off what Micah needed. Illiven, Blackhole people, are notoriously durable and strong, and if Micah could get this kid to do what he needs and the right way... they'll be able to get out of this hellhole once and for all.
[The details of the escape are a lot, enough that honestly, I could write a book about it, but I don't have that kinda time rn. What you need to know is that they did pull it off. Half Brute forcing their way out, half espionage and sneaky tactics and distractions. Destroying a lot of property to escape the wicked labs.]
The harsh sting of Merzen's air was honestly refreshing to the Rat. It's been so long since he's been out, yet he remembered it so vividly. The rot in the air from the surplus pollutants, the grey overhead and concrete jungle, the artificial light breathing some life into the city under the city's upper layers.
Home.

From there, Austin and Micah became a lot closer as friends, giving aide to one another without question, but in the end did go off to lead their own lives until they cross paths again. Austin went back to his home, Micah went off to form his own life. As now he's something different than the sewer rat he used to be. While he was doing so, he found out very interesting things about himself, one of which being the ability to communicate with the other rats perfectly.
Using that, he became Merzen's unofficial Rat King.