The only 5-letter word that means “halfgod” is satyr. A satyr is a creature in Greek mythology that is half-man and half-goat. They are often depicted as being lustful and mischievous.
Here are some other words that are related to “halfgod” and have 5 letters:
- demon – a supernatural being that is often considered to be evil
- nymph – a female spirit of nature
- titan – a giant in Greek mythology
- titaness – a female titan
- vixen – a female fox
Which word is the best fit for your context depends on the specific meaning you are looking for.