Merch (as he's usually called) looks pretty much exactly like his in-game character model, with long black hair, a goatee, blue eyes (or eye, rather), and pale skin. However, he's missing about half of his left ear, and his right eye. The right side of his face is scarred, pitted like it had been burned or melted, and it extends from just below his brow to his jaw line, and from the middle of his cheekbone all the way back to his earlobe. He has no piercings, but does have tattoos (See picture; those aren't complete, however). seeing as they're mostly on his chest and back, they're rarely seen, save for when he's wearing some open-fronted thing.
When in cities or on his off time, he can be seen wandering about, usually in light-weight armor. He seems to prefer his kilt to pants, and doesn't often show much skin, not even his hands. When they are shown, however, one can see slight callouses and old burn scars.
His armor and clothing is well-cared for, and usually only scuffed or dented when he's just come out of battle. He cares for his weapons and armor with an almost religious fervor, always cleaning them off and checking them for nicks and dings at the end of the day. He keeps himself clean, prefering to not smell like the Scourge he so often fights every day. He doesn't usually have any particular smell or scent about him, and he'd prefer to keep it that way. It's no good trying to fight an enemy that can smell you coming, no matter how good the smell is!
As mentioned in the summary, he's a loyal, fairly friendly individual, but is subject to bouts of paranoia and general distrust. He's somewhat conflicted, often forgets things, and is at times socially inept, sometimes bringing entire conversations to a halt, and then feeling tremendously bad about it. He seeks approval from those he values, such as friends, family, lovers, and those he looks up too. He can become upset when he doesn't have that approval, and become quite pouty and broody about it before actually attempting to right things. He can at times be childish and selfish, and his moods can change suddenly for seemingly no reason, within a split second, but he finds it difficult to stay angry or hold a grudge, and a simple change of atmosphere can at times be all that's needed to bring him out of a sullen mood.
He's usually quite laid back, even lazy at times, but is quick to lend his axe where it's needed, and eager to defend those he loves...sometimes, too eager. He's at least once alienated another Nether when he thought they were a threat to the guild, and thus his family, even though that Nether was previously a close friend, and though he's learned from that experience, he'll not hesitate to do it again should someone prove to be an actual threat, no matter who it is. He's slowly learning to live and let live, and to not stick his nose in other people's business unless invited too.
Never quick to actual, real, punch-throwing anger, it's hard to get him truly riled if one doesn't know him well enough to know which buttons to push. He tends to ignore rude individuals and troublemakers, though anyone that physically assaults him will have their actions returned in kind.
Most of his history before the Scourge, or even before his becoming a Death Knight is now, for the most part, irrelevant. After the Scourge, he became a Warlock and came to be in the employ of the Fist of the Horde. He rose quickly in the ranks until he was promoted to General, and there he stayed until his expedition to Northrend with his sister Cassea. During said expedition, he became lost, and was promptly attacked and captured by the Scourge and risen as a Death Knight, then sent to Acherus for training. During his stay there, the Fist was wiped out, and upon his return he found out none of his 'family' remained save for Cassea. His mental state was shakey at best to begin with, and this little nugget of information broke what little sanity he had left. He became massively paranoid, and had delusions about the Scourge being after his sister, and that EVERYONE was Scourge, and thus where ever Cassea went, she'd never be safe. He hallucinated ghouls, wraiths and geists constantly following him, voices commanding him to do things...Eventually he kidnapped his sister and held her against her will in a crypt in the Badlands, believing this the only way to keep her safe. This of course did not go over well with the other Nethers, and they were eventually found. Cassea managed to convince Merchea to come to Shattrath and speak with A'dal; otherwise, the only other option for him was death. Trusting her (and only her), he agreed, and the Na'aru healed his mind.
Now relatively normal and entertaining no agenda of kidnapping anyone anymore, he's now an Overseer of the Grizzly Hills for the Netherborne and doing quite well, though his mental state is still somewhat shakey at times...not that he'd let anyone in on that.