In this kind of fanfiction, there are often the main hypnotizer characters. They are usually portrayed as having strong willpower and some kind of special ability to hypnotize vampires. The vampire slaves themselves are important characters. They can range from newly - turned vampires who are more vulnerable to hypnosis to older, more powerful vampires who have been subdued in some way. And don't forget the side characters. There could be a seer who foresees the fate of the vampire slaves or a vampire hunter who gets involved in the situation for his own reasons, like trying to use the situation to his advantage or having a moral obligation to stop the hypnosis.
The themes in 'hipnotized vampire slaves fanfiction' can be quite diverse. For example, the exploration of the vampires' special abilities under hypnosis. Are they still able to use their powers like super strength or mind - reading? It could also focus on the moral implications of having vampire slaves. Is it right or wrong? And then there's the theme of redemption. Can a vampire slave who has been made to do bad things while hypnotized find a way to redeem themselves? This can lead to very interesting character - driven storylines.
It might be an abbreviation for a name, like 'David X. Doe' or something similar. Or it could be a unique name within a specific group or community that is into fanfiction. Maybe it's a code name for a person who reviews fanfiction. Without more context, it's really hard to say for sure.
You can try websites like Fanfiction.net. It has a large collection of fan - made stories for various series, including Highschool DxD. Just search for 'Highschool DxD Vali' and you'll get a list of relevant fanfictions.
One popular fanfiction might be those that explore Vali's backstory more in - depth. For example, stories could detail his training and how he became so powerful.
I'm not entirely sure specifically what 'dxd adult fanfic' is. 'DxD' might refer to a particular series (such as 'High School DxD'), and 'fanfic' stands for fan fiction. However, the 'adult' part implies it could be fan - created stories with mature or inappropriate content which is not suitable to discuss in detail.
The number of DxD novels can be a bit tricky to pin down. Different regions might have different releases and editions. Your best bet is to do a comprehensive search on popular book databases or consult with avid fans of the series.
The Highschool DxD manga has indeed finished. It wrapped up after completing all the planned story arcs and providing a satisfying conclusion for the readers.