As a Fridge subpage, all spoilers are unmarked as per policy. You Have Been Warned.
- Those who were curious enough to Google the lyrics to Diva's aria (we don't blame you) found out that the words were nothing but gibberish. This perfectly illustrates Diva's background. Because she was only given the bare minimum to survive, she never had the chance to go to school like Saya did, and thus never learned human language until much later in her life. By then, she was already singing this song, which reflects her anger, frustration, and downright depression from the way the first Joel and Amshel treated her.
- A major part of Diva's motivation throughout the series in her attacks against Saya, Kai, and Riku. It should be remembered that Diva was jealous of the affection Saya received from Joel I, while Diva was treated like a lab rat, and that Diva wanted a family of her own. In the present time, Diva had her chevaliers, but Saya had Kai and Riku, her brothers (George having died prior to Diva's awakening). Diva's jealousy explains her motivations in many of her actions. First, her attack on Riku at the Zoo: Riku finds her and calls out Saya's name, seemingly happy to see her (in the original, his relationship with Saya is explicitly made clear to Diva, calling her "Saya-neechan" note ). The next scene we see is Diva drinking his blood, then singing and dancing with his unconscious body in front of Saya before gloating about how delicious he was. Anyone with a brother or sister would find elements of this scene familiar (substituting a broken toy or stolen food for a dead or near-dead loved one). Next, we have the rape/murder of Riku. Note that, despite Hagi having been around from the beginning, there is no indication that Diva has ever sought him out. This could be because Hagi was not as helpless as Riku, or the connection between Diva and Riku that derived from her draining him at the Zoo; but it could also result from the fact that Riku was Saya's brother, while Hagi was just her chevalier (and, of course, Diva had plenty of chevaliers, so her jealousy didn't extend there). To Diva, it would have seemed fitting that, in raping and murdering Riku, the same act that gave her a family would deprive Saya of hers. (Recall that, immediately after the murder, Diva was on the point of making Kai her chevalier.) In a later episode, Diva makes a renewed effort to persuade Kai to willingly become her chevalier. Diva's success at either time would have served a twofold purpose: taking Kai away from Saya, finishing the destruction of her family, and twisting the knife even further by setting up a situation where Saya might have to kill Kai. Thus, Diva's overarching motivation throughout the series was not only to have her own family, but to destroy Saya's family out of jealousy at being denied her own for so long.
- Adding to the above: Why does Diva rape and kill Riku? Because Riku was the most innocent hearten member of Saya's family. He represents the important thing she had taken from her in the past. This is why she kills him also. It's wasn't just to hurt Saya, it was because Riku's innocence was gone after the horrible deed. She rapes and kills him in an attempt to reclaim her innocence, which is why she lets herself get impregnated by him. She wanted her children to be innocent with a clean slate, and not a monster like her. This is reinforced by her making herself to look like Riku for the remainder of the series. It wasn't just to torment Saya, it was also because she was longing for the innocence he represented in her mind. This is why she really doesn't care for her chiropteran servants. Diva's actions throughout the series is motivated by hurt, envy, and revenge. She wanted to have the same life as Saya, and never wanted the life that was forced upon her.
- Saya's hate for the chiropteran can be explained by the fact that they are part of Diva's brood. That the chiropteran works like that is almost similar to Tokyo Ghoul. They need to be able to diminish their own numbers or the humans they hunt will go extinct.
- Nathan's death, or lack of it, could be explained if he really is Saya's and Diva's Mother's chevalier. Since one queen's blood kills the other and vice versa, one that stems from a bond before the queens would be immune to both their blood. It also explains his attitude towards them. For him, it is just a minor fight between siblings which he will come out on top of no matter who wins.
- The blood-drinking chiropteran queens are born as twins, always one red-eyed and one blue-eyed, with the chiropteran they go on to make also exhibiting these eye colors after transformation. In the circulatory system, blood is red and the veins that carry it are blue.
- This Tumblr theory about the anime's ending positing that Hagi really was Killed Off for Real in the series finale and that the rose with his ribbon at Saya's crypt was left there by Nathan, getting ready to impersonate Hagi and take his place when she wakes up.
- Not true. Blood # reveals that Hagi is alive and well, unless you're ignoring Blood #.
- The way that Riku died after his untimely raping. In order for someone with Saya's blood to die for good, Diva's blood has to mix with it, causing every part full of blood in their body to crystallize violently. Diva had to rape Riku badly enough to make him bleed, likely from the mouth or genitals— and he likely fought back, causing Diva to bleed as well. Their blood mixed, and Riku was dead as a doornail within minutes.