A dope fiend.
A crossword-puzzle fiend.
A fiend with computers.
Fiended for the band's new release.
An example of a fiend is someone who does a lot of drugs (a drug fiend).
An example of a fiend is a constant shopper.
An example of a fiend is someone who is not kind to animals.
A fresh-air fiend.
A fiend at tennis.
A jazz fiend.