The unlisted Demon Races that are from Kiva databook. Supposedly people translate them from a Japanese wiki but I'd like some experts on this site verify it if it's true.
Mermaids are female counterparts of the Merman and who they breed with to increase numbers. Unlike their male counterparts, they survived the purge from the Fangire but are hunted by humans and their numbers dwindle due to the extinction of the Merman race.
Ghosts are non-corporeal beings and they drain life force by inhaling it.
Gigants are ten feet tall monsters, they survived the purge. Their sub-species are Cyclops and a Yeti. The Yeti is actually captured and studied to create the Kamen Rider Rey system.
Hobbits are 10-centimeter tall dwarfen beings. They're pacifistic farmers who live in the woods and survived extinction by submitting to the Fangire rule as slaves.
Goblins are cruel creatures who eat flesh of their enemies and enjoy collecting bones. They were wiped out by the forces led by the First King wearing the Saga armor.
Sagarc are actually sub-species of one of the Demon Races. Probably Kivat. And humans are indeed one of the thirteen races.