Nintendo has a line of Demon Hunter games. D&D has a class Demon Hunter.
Fwiw, games and video games fall into difference Nice classes (commercial areas of application of trade marks). Without those things being international household names in and of themselves then it's not relevant; unless you were saying that Nintendo or a D&D company had registered the trade marks for music already.
Not only do you not know what makes a potential trade mark generic, but you don't know what a straw man is either ...
You're sort of right about the names, but know of standing in this case has the given name "Demon Hunter", it's a band name.
Trade mark is a registered IP right, it doesn't matter if you intended to infringe it, you can't trade using someone else's registered name (in the same field of commerce, and same geographic area).