Well… split is probably too harsh. Some guys who were somewhat considered as “exclusive” artists and writers the studio commissioned, suddenly became independent and created a doujin studio that made Corpse Maid. For a while, BCyc was experimenting with different presentations of of dark eroge, while Corpse Maid followed the “MinDead/EXTRAVAGANZA” type thing. A bit later they were back with BCyc hiring them.
Could have just been a period, where they took a break and recharged their batteries: though their sudden departure, immediate work an eroge, and return back doesn’t exactly seem like it. Either way… Mugen Kairou 2 and even Cthulhu, show the company still has the creativity… just that they’re not on a roll.
As the others mention: depends what kind of “dark” we’re talking about. Draculius from meromero cute is a dark eroge, but so is Devils Devel Concept from Akatsuki Work, Tsukihime from Type Moon, Sabae no Ou from Lost Script, and of course MinDeaD BlooD from Black Cyc. The way they handle “dark content” is as varied as they handle vampires.
One can like all of them (I do) - and some may only like one or two of them.
BCyc has become known for taking violent sex and over-the-top tentacle rape, making it a central selling point for the title, but still provide a solid supernatural scenario, so that there’s more to talk about than the sex. They’re also known for making games overboard challenging for a 100% complete, and contracting Death Neko music for their “big budget titles” (Denkishiki Karen Ongaku Shuudan, who is really Y?sei Teikoku).