Here is a preliminary background for Markus:
Markus grew up on the banks of the Adamant Sea. Raised the son of a healer, he learned the basics at an early age. As time went on though, he became fascinated with the way fingers and even whole limbs could be reattached with limited success. He got good at it as he practiced. Eventually the idea of attaching a limb that was from a different creature struck him. He didn't have a chance to delve into this idea for quite some time. However, the coastal village where he was living was attacked by a rash of monstrous crabs over the course of a few weeks. During one of these attacks, one of the monsters managed to get its claw around his forearm, and he lost his left arm below the elbow. For many, this would have been a travesty, but Markus looked on the extent with cold intellect. He saw it as an opportunity. The villagers managed to kill one of the crabs a few days latter, and Markus was able to get ahold of the claw that severed his arm. Many thought he was going to mount it on the wall as a sort of trophy over the monster. Markus though had other ideas. He grafted the claw onto his stump. Miraculously, or abhorrently as many would say, the graft took. Markus hide the graft as best he could for a while, happy to have successfully managed it. But when the other villagers discovered his secret, he was forced out of the town. Now, Markus seeks a quite place to continue his experiments. Knowing what is possible though, he also hopes to find other creatures to steal body parts from. 'The Claw was interesting, and a proof of concept, but what else could his body handle?' he wonders.