I'm not sure specifically as I haven't read this particular fanfic. But generally, it might be about a character named Harry who is portrayed as the Angel of Death in the context of the Supernatural universe. Maybe it involves Harry having powers related to death, like being able to reap souls or having some sort of connection to the afterlife.
You could start by looking on popular fanfic websites such as Archive of Our Own (AO3). It has a large collection of Supernatural fanfics, and there's a good chance you'll find this one there.
I'm not sure specifically as I haven't read that particular fanfic. It might be about Harry having some connection to the concept of the angel of death, perhaps he takes on a role related to death in some sort of alternate universe or fan - created scenario.
Definitely Castiel. Castiel has his own complex relationship with death and the divine in the Supernatural world. Pairing him with the Angel of Death would create a really interesting dynamic. They both have different views on mortality and the afterlife, which could lead to some great character interactions.
Obviously, Harry is one of the main characters since he's in the title. But without reading it, it's hard to say who else might be in it. There could be characters from the original source material that the fanfic is based on, like his friends or enemies. Maybe there are also new characters created specifically for this fanfic that interact with Harry in his role as the angel of death.
It's difficult to say precisely. But it might be a story where the idea of death is explored through the lens of the two fandoms. In 'Harry Potter', death has a certain set of rules and significance, and in 'Supernatural' there are different takes on the afterlife and death. This fanfic could be about a character's journey through death or their attempts to cheat it, using the unique elements from both the 'Harry Potter' and 'Supernatural' universes. It could also be a story about how the two different views of death in these universes collide or interact.
Some common themes include the power dynamics. The Angel of Death is extremely powerful, and fanfictions often explore how this power is perceived and dealt with by other characters. There's also the theme of redemption. Maybe the Angel of Death has made mistakes in the past and is seeking to make amends. And of course, love and friendship can be themes too. They could develop a bond with a human or another supernatural being that challenges their original purpose.
A common theme is power and its consequences. Since Harry is the master of death, he has a great deal of power, and fanfics often explore how he uses or is tempted by it. Another theme is the blurring of boundaries between the known magical world in Harry Potter and the added supernatural elements.
Yes. In some ways, Harry Potter can be seen as having elements related to death and the supernatural. The presence of magic, dark wizards, and the concept of the afterlife in the series all touch on supernatural themes. And death is a major theme throughout the books, from the death of Harry's parents to the many battles and sacrifices that occur.
There are quite a few. You can start by looking on fanfiction websites like FanFiction.net or Archive of Our Own. Some might explore the concept of an Angel of Death in the context of the Harry Potter universe in very creative ways, such as how it might interact with the characters' fates or the magic system.