Mythological creatures, or creatures you've invented, don't need to be capitalised, just like real-life animals. There's no grammatical difference between "a dog", "an orc", "a dragon" and "a manananggal".
Are creatures capitalized?
Are Animal Names Capitalized? Capitalize animal names if they are proper nouns. However, do not capitalize common nouns.
What words Cannot be capitalized?
Words Which Should Not Be Capitalized in a Title
- Articles: a, an, & the.
- Coordinate conjunctions: for, and, nor, but, or, yet & so (FANBOYS).
- Prepositions, such as at, around, by, after, along, for, from, of, on, to, with & without.
