Learning Greek

I'm making a monster name generator for my game. Traditionally video game monsters have Greek names. So I need to know basic Greek inflection rules to turn noun into an adjective, suitable for monster name. For example greek word for gold is "chrysos" (yes, Jesus Christ got greek surname). Now would "chrysis" be the correct word for golden? Now Google Translate claims it is chrysafenous, but I'm dead sure the ancient Greek word for "golden" is "chrysis", and google translate also translates "chrysis" as "golden". WTF is with that chrysafenous?

Traditionally video game monsters have Greek names

Really? I thought it was whatever post-Tolkein, gnostic, fantasy schlock bs Nip game devs think sound cool.

Vernacular and grammar isn't really learning the language though. I mean, like, it is a dead language, so you can't use it and therefore can't learn it per se. In a similar sense, I know English, but I don't have formal knowledge of etymology and grammar. Understanding a language formally is pretty much a separate thing. Just being pedantic, though.