* A misspelling: Perhaps you meant "demonical" or "demonic", both of which refer to something related to demons or having the characteristics of a demon, such as being evil, malevolent, or supernatural.
* A neologism: Someone might have created "demonica" as a new word, perhaps as a noun to describe something related to demons or as an adjective meaning "demon-like".
* A specific term: It could be a word used in a particular context or field, such as a specific genre of fiction or music, or within a specific subculture.
To understand the meaning of "demonica", please provide more context. For example:
* Where did you encounter this word? (a book, a song, a website, etc.)
* What was the sentence or situation where it was used?
This will help me understand what you mean and give you a more accurate answer.