It means that "lol I wanna put Yu-Gi-Oh God Card characters into a game that has nothing in common with Yu-Gi-Oh besides an Egyptian setting because I don't like what exists there currently and shoehorning in deific characters from a completely different series and time period is obviously a fantastic idea and wouldn't cause any sort of continuity or plot-quality issues whatsoever" is the kind of idea an eleven-year-old fanboy of a TCG series comes up with because he thinks his card games are the greatest thing ever conceived and tries to insert them into anything else regardless of whether it even makes sense or not.
Oh, and just for the record--an ancient Egyptian-esque setting doesn't mean fucking Yu-Gi-Oh characters are "better." You do realize that they made a solid 90% of that shit up for the series, right? Slifer's a six-hundred-degrees-of-separated reference to Osiris and named after a 4Kids employee, Obelisk is a generic anime spikey buff dude named after a pointed monolith, and Ra is a barely-accurate representation of said god's ba, which was essentially a phoenix--ain't shit related to the actual deity that has anything to do with dragons as most of the world represents them.
Meanwhile, Astarte is the Hellenized name for Ishtar, a deity directly associated with sexuality and war, and who also was worshiped throughout Egypt once the Levantines showed up there.
Wonder which of the two has more genuine ties to ancient Egyptian cultures, the actual goddess from actual sects being represented as a highly attractive female warrior who clearly uses her sexuality to charm the male character, or the big OP god-monsters who stand as distant bastardized references to actual elements of that same culture? Hmmmmm, such a tough call, that.
That's what Weapon means by that--it's an idea rather clearly based out of personal preferences and seeming fanboyism rather than actual attempts to reference actual mythology as the series has always done.
All right, get this, but I would prefer Castlevania over Yugioh. So don't call me a Yugioh fanboy. It's one of my minor hobbies. Castlevania would be one of my major hobby.
First of all, 4kids ver is shitty butchered version like SNES Rondo. You really should see original JP version to say anything. Also, I only want to change the Sandy grave boss because Astarte is one of most shittiest Castlevania boss, not because I wan't to squeeze Yugioh into this. I would leave others out. Also, Sandy Grave boss has nothing to do with plot of the game and I would put this as a crossover of two series rather then squishing this into the plot line. Astarte would be nice for a random mediocre anime game, but not CASTLEVANIA!
Also, Castlevania doesn't need to be that accurate with history (like Charlotte's kind of miniskirts weren't invented till 50s and it would be a better idea to wear loose pants), also, bad-ass looking powerful god monsters are more suitable for a "boss" then a... sorry, but
I think bit of creative looseness would be allowed to make this whole lot better. Also, Konami has rights for both, so there wouldn't be a problem. Also, if this doesn't work, they could use some other powerful-looking (actual) Egyptian gods like Sun god Ra, Death god Osiris or Guardian Deity Horus, anything but a fxcking Sex god Astarte!