It could be some jealous Fae who don't like Bo having a half - human baby. They might see it as a threat to the Fae purity or something.
Maybe a group of scientists who had been secretly studying Lauren and want to get their hands on the baby to study its genetics. Since Lauren has been involved in some unique medical and scientific things, they think the baby could hold the key to some great discovery.
There could be a dark Fae entity that feeds on the innocence of new - borns. It senses the power within Bo and Lauren's baby and tries to take it away. This would create a great conflict for Bo and Lauren as they fight to protect their child from this menacing force.
One possible plot could be that Bo and Lauren face challenges in raising the baby while also dealing with the supernatural elements in their world. Maybe the baby has some unique powers that attract unwanted attention from evil forces.
It could be some of the traditional antagonists from the original story, like the Volturi. They might see the baby as a threat to their power or the order they've established in the vampire world.
One possible antagonist could be an evil scientist who wants to study the baby's unique genetic makeup. Since Shadow and Blaze are both special characters, their baby would likely have an interesting genetic combination that the scientist could use for his own malicious purposes.
Maybe there are some secret organizations that want to study the baby because it's a hybrid of Ben and Gwen's powers. These organizations might not have evil intentions at first, but their methods of trying to get the baby could make them antagonists as they go against Ben and Gwen's wishes to protect their child.
It could be the other spirits in the house who are jealous of the new life Tate and Violet are bringing into the world. They might try to cause trouble or harm to the baby out of envy.
It could be a jealous ex - partner of either Derek or Chloe. This person might try to create problems between them during the pregnancy, like spreading false rumors or causing misunderstandings.
The other gods who oppose the union of a mortal (or demigod in Percy's case) and a goddess could be antagonists. They might see the baby as an abomination or a threat to the order of the divine world. For example, some of the more traditional and strict gods could try to harm the baby or separate Percy and Hestia.
The old enemies of Fox, such as Andross' remaining followers could be antagonists. They might see the baby as a new target to get back at Fox for all the defeats they suffered in the past.
It could be Bowser. He might see the new baby as a way to get to Daisy and Luigi. He could try to kidnap the baby to use as leverage against them.
The Volturi could be antagonists. Since they are the vampire authority, they might see the baby as a threat to the vampire world order. They could be worried about the baby's mixed heritage and its potential power, so they might try to eliminate the baby and even Bella and Klaus. Another possible antagonist could be some of Klaus's old enemies. They might see the baby as a way to get revenge on Klaus, either by kidnapping the baby or causing harm to it and its parents.