Love and romance are also very common. Usually, there is a love interest, often a human, which adds a layer of complexity to the story. For example, in many such novels, the vampire has to protect their human love from other vampires or from the knowledge of their true nature. It's about the forbidden love aspect. And there's often a theme of power. Vampires are typically powerful creatures, and the main character might be dealing with how to use or control their power, or they might be in a power struggle with other vampires in the story.
One popular 'Vampire MC Light Novel' is 'Vampire Knight'. It has an engaging story with a vampire main character in a school setting filled with mystery and romance.
Another aspect is prior knowledge or experience. In some light novels, the MC is reincarnated or transferred from another world. Like in 'Konosuba', Kazuma has knowledge from his previous life which he uses to his advantage in the new world, and this knowledge combined with his unique skills makes him overpowered in certain situations.
I'm not aware of a specific 'mc as robot light novel' to base similar recommendations on. But some general robot - themed light novels could be interesting. For example, 'Full Metal Panic!' has elements related to mecha and robots, though the main character isn't exactly a robot but has a lot to do with them.
A mentor figure could be the one betraying the mc. The mc trusted this mentor completely, but the mentor has some hidden motives. Maybe they are working for a greater evil and see the mc as a threat or a tool to be used, so they betray the mc, which then causes the mc to turn dark.
Since we don't have more details about the light novel, we can only assume general things about the mc. The mc might be a person with a special ability or background that allows them to obtain and utilize liquid x. It could be that they have a unique heritage that gives them access to this monster - repelling liquid. Or perhaps they stumbled upon it during their travels and figured out its use through trial and error. The mc is the key player in this story who uses liquid x to fend off the monsters and drive the plot forward.
Well, a 'demon mc light novel' could involve a story where the demon main character has some kind of special power or ability. It might be set in a fantasy world filled with other magical creatures. Maybe the demon is on a quest to gain more power, or it could be trying to overcome some prejudice from other races in that fictional world. There could also be elements of mystery and intrigue as the demon uncovers secrets about its own past or the world around it.
One popular one is 'Overlord'. The main character Momonga is extremely overpowered. He starts as a max - level player in a game and when the game world turns into a real one, his abilities are far beyond others. His magic powers and strategic mind make him nearly unbeatable.
I'm not sure specifically as there could be many different 'mc as robot' light novels. It might be about a main character (mc) who is transformed into a robot and then experiences various adventures, like dealing with a new robotic form, interacting with other characters in a world where robots are perhaps not the norm, or facing challenges related to the new identity.