Here are monster are owned by Toho but are not Godzilla related monster, non-Toho monster, unused Monsters that are scrapped, video game only Monsters, and American made monsters. The only exception is Kong, Mechani-Kong, and Skull-crawlers since I would use those two last monster for Kong: King Of The Apes. They be heroic Kaiju or villainous ones
10. Cretaceous/Grand King Ghidorah
A Space Hydra Kaiju who is an enemy of Devine Moths and the ancestor of the current King Ghidorah. His first appearance is Rebirth of Mothra (1998). His origin that he is a space monster like his successor King Ghidorah but instead of civilization he destroy, he feast on the life force of many lifeform from prehistoric time then evolved to his current form to feast on humans.
9. Toto
A Turtle Kaiju who is the son of the original Gamera in the last Heisei movies or only Millennium series. His first appearance Gamera The Brave (2006). His origin that Gamera laid an egg before he self-destruct himself, the egg was founded by a boy he kept him as a pet then realized it not a normal turtle.
8. Death Ghidorah
Another Space Hydra Kaiju who is also an enemy of Devine Moths and a relative of Grand King Ghidorah. His first appearance is Rebirth of Mothra (1996). His origin is similar to other Ghidorahs but while destroy Venus civilization, he was on Mars turning wasteland million of years ago.
7. Gyaos
A species of Bat/Bird-like Kaiju who is the archenemy and recurring monster in the Gamera movies. It first appearance Gamera vs. Gyaos (1967). Their origin is that they were created by the people of Atlantis then they turn on their creator, the original species died out but lay egg which will hatch in a change Earth.
6. Clover
An Undersea Kaiju who originated in his own movie series owned by Bad Robot. His first appearance is Cloverfield (2008). His origin is that he a deep sea monster who lay dormant until he was awaken by a submarine, he is actually a juvenile.
5. Bagan
An Ancient Kaiju who been scrapped multiple times until he made his focus appearance in a video game. His first intended appear is the scrapped Resurrection of Godzilla ( Early 1980s) while actually appearance is the SNES game Super Godzilla (1993). His origin he's an ancient creature from China who brought in the past by aliens to genetically modified him with Godzilla and King Ghidorah genes.
4. MUTOs
A pair of Parasitic Kaiju who originated in the MonsterVerse owned by Legendary. Their first appearance is Godzilla (2014). The pair origins is that they were prehistoric creatures that feed on radiation, the gender originated from different places but will come together to mate and reproduce more of their kind.
3. Mothra Leo
A Moth Kaiju who originated in a Toho Trilogy movie starring Devine Moths and the son of Mothra. His first appearance is Rebirth of Mothra (1996). His origin that Mothra laid an egg before she died out, with her son taking the role as God of Infant Island and guardian of the Earth to fight the Ghidorah alien species.
2. Frankenstein
A Humanoid Kaiju who originated from the German story book & famous movie monster which is owned by Universal. His first appearance is the novel Frankenstein (1818), for the famous film is Frankenstein (1931), then use by Toho in Frankenstein vs. Baragon (1965). His origin in most media is that he is created by the mad scientist Dr. Victor Frankenstein in hope to create life, Toho's version is similar but die and revived for decades then later in the years exposed by nuclear energy to slowly grow it from a little boy to a monster.
1. Gamera
Another Turtle Kaiju owned and created by Toho's company rival Daiei until it was bought by Kadokawa to form into one. His first appearance in Gamera, The Giant Monsters (1965). His origin is that he was created by the Atlanteans to fight off their previous creation Gyaos, there were four of Gamera's species but live.
Secret 11. MechaMothra
A Cyborg Moth Kaiju who was scrapped and later be replaced by the Heisei Mechagodzilla. Her intended appear is a sequel for Godzilla vs. Mothra (1994). Her origin is that Mothra was recovered and turned into a cyborg and seem to be more a dragonfly.
Honorable mentions
Barugon
H-Man
Human Vapor
Telegian
Zedus
Iris
Griffin
Legion