Ikenie

Both are adult oriented stories about the mistreatment of women during the middle ages by the corrupt church. In Belladonna's case it's a pact with the devil, in Ikenie it's a succubus fantasy of a church related artist. In both cases there's rape of an innocent woman, who is then blamed of witchcraft and punished to cover up. Both have a hentai tag, but can be watched for the story alone. 

Dark atmosphere and mysteries + both hentai suggest that every person has a dark side =))) 

Both are related to demons, Heaven and Hell, and bringing out the dark side in someone. Though Ikenie does not contain magic and Bible Black does, Ikenie does somewhat suggest that magic may be possible in that world. Bible Black is much more in depth in story and is a lot longer than Ikenie, but if you like dark animes that are focussed around demonic presences and good vs evil, you'll probably like both.