I'm not entirely sure as I haven't read it specifically. But generally, it might be about a black obelisk which could be a central mystery, a symbol, or an object around which the story's plot, characters, and events revolve.
In a yandere phobos x will fanfic, one aspect to consider is the power dynamic. If Phobos has more power, it can intensify his yandere tendencies. For example, he could use his influence to isolate Will. The fic might also focus on Will's reaction to Phobos' yandere behavior. Will could either be scared or, in an interesting twist, gradually come to understand and even accept Phobos in some way.
Look for fanfic communities dedicated to the source material that Phobos and Will are from. There, you can ask for recommendations of 'yandere phobos x will fanfic'. Members are usually quite helpful in sharing their favorite stories in this genre.
I'm not aware of the author of this 'Phobos King of Beasts' novel. It could be an indie author or someone from a relatively unknown publisher. Without more information, it's impossible to determine the author.
One possible plot could be that they kidnap a character to gain some sort of power. Maybe they think the kidnapped character has a special ability or knowledge that they need. For example, if it's in a superhero - themed fanfiction, the kidnapped character might be able to control an element, and Will and Phobos want to use that power for their own evil plans.
It could be a young and innocent bystander. Maybe someone who was just in the wrong place at the wrong time. For instance, a small child who happened to be near where Will and Phobos were planning their kidnapping and was grabbed instead of their intended target.
One likely antagonist could be those who oppose Naruto having the power of Obelisk the Tormentor. They might see it as a threat to their own power or plans. Maybe some of the rogue ninja groups or even some of the hidden villages that have their own agendas.
Well, it could be that Naruto somehow discovers the power of Obelisk the Tormentor. Maybe he stumbles upon an ancient relic or meets a mysterious figure who bestows this power upon him. Then he has to learn to control it, which might be really difficult as Obelisk the Tormentor's power is extremely potent.
It depends. Sometimes it might be possible, but it often depends on the specific rules and mechanics of the story or the game where the obelisk is involved.