Well that’s the question, isn’t it? Both dungeons and dragons are common words, but put them together and you have a brand name. Micro and soft are normal words. Star and Wars are!
My go-to is always to either look for prominent examples in unaffiliated fiction that also use the combined structure (as with McCaffrey's color-coded dragons above) or determine if referring to the creature with modifiers of this type has mythological precedent. Golems, for example, are
most strongly associated with clay, but they can be made from all sorts of things, including mud and stone, so long as the material itself is inanimate. Further, referring to creatures as "<material> golem" is quite common in other fantasy works that aren't controlled in any way by the D&D rights-holder: Blizzard's Warcraft series and ArenaNet's Guild Wars (the original) has flesh golems, for example.
Hence, referring to an artificially-constructed being animated through supernatural means (whether necromantic or "merely" magical/divine) as a "<material> golem" is probably not copyright-able due to both historical precedent
and competitors using the terms as they like.
But even there, it's worth being cautious. Aurene (a character from Guild Wars 2) and her siblings/mother/grandfather are all crystalline dragons who specifically have crystalline and (to a certain extent) mental powers, but I don't know if that's enough to justify the claim that "crystal" dragons work. If beefed up with a few more examples, e.g. Smaug being known for having a gem-encrusted hide and (say) finding evidence of ancient Asian stories involving ruby-colored dragons, then I could see some room for it. Alternatively, again to cite WoW, there's the Emerald Dragonflight (an alternate name for the Green Dragonflight), recognizing that some types of dragons are seen as having jewel-like scales. There's also the
Black Jewels series, where the titular jewels (spoiler alert)
are discovered to actually be dragon scales, which manifest either as finger-sized "uncut" jewels or roughly thumbnail-sized "cut" jewels after certain coming-of-age ceremonies, and thus provide a link between "gems" and "dragons."
