To Light a Candle
He didn't lose a hand, he gained a grudge.
Hampus was brought into the fold of the Lucifuge by Costello during his time in Europe. Hampus didn’t come willingly, at first.
Only after he had been properly trained was he given a prosthetic to replace the hand Costello had shot off. Out of all the much more suitable choices, he picked an older model with two hooks that could be used for basic gripping motions.
He said it served his purposes just fine.