Filch came to The Grey Rover six years ago under Old Captain Pete. He hid in a dinghy, white as a sheet and shaking with fear, and he wasn't discovered until the shore party made it back to the ship. He didn't say much to anyone, but he nodded when Pete offered him a job.
His skill with his hands served the crew well. Whenever the captain asked, he could pilfer a key from anyone and melt into the shadows. He never told anyone his name, so he earned the name Filch. He seems to like it, or maybe he just enjoys the anonymity of an alias. The ship's healer Vadym couldn't find anything wrong with him. Pike seemed to recognize something broken within him, and they silently bonded over their individual traumas.
When Pete got captured and the captain's job brought the crew to blows, Oya Stormqueen went out of her way to ask Filch what he thought. He shrugged as usual, but seemed to follow her lead from then on. Filch landed a stunning blow on the main opposition, allowing Oya to claim victory and start letting resentful crew members leave the ship. He received a promotion to Lieutenant for helping Oya win over the crew.
Filch will actually smile and occasionally chat now, allowing glimmers of his old overconfident self through whatever fear caused him to lock himself away. He still doesn't talk about his past, and he still has a hard time taking the initiative to do anything, but if given a task he will get it done quickly and thoroughly. He knows quite a bit of esoteric knowledge about magic and nature, and he works well in both wilderness and dungeon situations.
Filch still looks like a boy, but he's nearly 30. His green eyes, red hair, and freckles mark him as a son of one of the clans in Dunhill, but nobody seems to have missed him over the years. He stands shorter and thinner than many, and his ability with locks and traps have saved the crew on more than one occasion.
Note: I'm not sure what scared the hell out of Filch yet myself, so I'll leave him as a mystery box to open later. He may have uncovered the Deepspeakers and the entity trapped beneath Fellport Harbor, or it could be a coven of mind flayers that ripped away some of his personality before he could escape. He's a GM tool for sure whenever it makes sense to unlock him.
Dunhill Human Scout Rogue (Level 4) (Charlatan Background; Dungeon Delver Feat)
Str 8 Dex 18 Con 14 Int 14 Wis 12 Cha 10
Acrobatics +6, Arcana +4, Deception +2, Investigation* +6, Nature* +6, Perception +3, Sleight of Hand* +8, Survival* +5, Stealth +6