One interesting plotline could be the encounter between Harry Potter and a demon god. Maybe the demon god has some connection to Voldemort, like being an ancient power that Voldemort tries to harness. Another could be Harry having to learn new magic to combat the demon god's dark powers. For example, he might discover ancient spells from Hogwarts' hidden archives.
Well, in some 'Harry Potter Demon God Fanfiction', a plotline could involve the demon god influencing the magical creatures in the wizarding world. The centaurs might start acting strangely, and Harry has to figure out if it's the demon god's doing. Also, the demon god could be using the Forbidden Forest as its lair, and Harry and his friends have to venture in there to stop it. They might encounter new and dangerous magical plants and beasts along the way.
One interesting plotline could be Harry having god - like powers and using them to change the wizarding world for the better. For example, he might be able to instantly end all forms of dark magic or create a utopia for magical creatures.
One interesting plotline could be the discovery of new magical abilities related to being the heir of God. For example, the character might be able to perform magic that is far beyond what normal wizards can do, like controlling natural elements in a much more powerful way. Maybe they can stop a raging storm or make plants grow instantly on a large scale.
One interesting plotline could be how Harry's magic is enhanced or different due to being raised by a god. Maybe his spells are more powerful or he has unique abilities that others don't. Another could be his relationship with the wizarding world. Since he was raised by a god, he might have a different perspective on the rules and traditions of the wizarding community.
One possible plotline could be Harry struggling to control his demon side while at Hogwarts. Maybe he has unexpected outbursts of power that draw the attention of both friends and foes.
One plotline might be that the dog demon is actually a cursed form of a wizard. In the fanfiction, it tries to find a way to break the curse while being in the midst of the Harry Potter universe. It could get help from Dumbledore or other powerful wizards. This would involve a lot of mystery and exploration of the magical lore of both the dog demon's nature and the wizarding world's magic.
In a 'Harry Potter is a Fox Demon fanfiction', the plot might start with Harry having strange dreams about fox demons. As he investigates, he finds out that his family has a long - lost connection to the fox demon realm. He then embarks on a journey to learn more about his heritage. Along the way, he meets other characters who are also related to fox demons in some way. They might form a group to fight against an evil force that is trying to use the power of fox demons for their own dark purposes. This could involve battles in both the wizarding world and the fox demon realm, with Harry having to use his knowledge of magic and his new fox demon abilities to protect his friends and the two worlds he now belongs to.
One possible plotline could be that Harry discovers his new 'God of Destruction' powers gradually. At first, he's scared and confused by them. But as he learns to control them, he uses them to fight against a new, even more powerful dark force that threatens the wizarding world and the Muggle world alike.
Well, some might involve magical creatures with furry characteristics in new adventures at Hogwarts. For example, a werewolf character could have a unique story arc that intersects with the main Harry Potter plot. Maybe they are trying to find a cure or dealing with the prejudice within the wizarding world in a different way than what's in the original books.
One possible plotline could be a comical take on baby Harry's magical mishaps. Maybe he accidentally makes his diapers levitate or turns his crib into a mini Hogwarts. Another could be about how the other characters like Hagrid or Dumbledore interact with baby Harry in this unique situation, perhaps trying to figure out how to handle his early magical outbursts while he's still in diapers.
Perhaps a plotline where the ogre has some sort of special power that the wizards in Harry Potter are interested in. This could lead to a whole series of events where they try to either control or cooperate with the ogre.