- Order: Saurischia
- Suborder: Wyvern Feet
- Infraorder: Heavy Shell Wyvern
- Superfamily: Armor Wyvern
- Family: Armor Wyvern
Gravios are apart of the Flying Wyvern classification. They are the adult form of the Basarios and are distant relatives of Monoblos, Diablos, and Varusaburosu. Its unknown if Gravios have subspecies, however, Black Gravios have been seen though they aren't subspecies of Gravios but just individuals that were badly burnt by lava while they were Basarios. Living in the Desert is Gravios' ancestor known as Gureadomosu.
Within the Old World Gravios is found roaming in the Swamp, Old Swamp, Volcano, Old Volcano, Everwood, Volcanic Hollow, Ingle Isle, and Primal Forest. Some Gravios have even been seen inside the mysterious Sky Corridor.
Gravios is easily one of the strongest wyverns found in either the swamp or volcanic regions. They feed heavily on volcanic rocks for minerals and ores, which consequently aid the development of their supremely strong shells, gases and fire beam but they will also occasionally eat meat. Gravios are known to migrate to the Swamps feed on ore and smaller species. The bulk of the Gravios is enough to discourage predation, as is its habits to travel using the lava systems of the Volcano. The Akantor is the only known true natural predator of the Gravios.
Among the largest of the Flying Wyverns, Gravios out-weighs its brethren but can still lift its bulk for a limited time using its wings. Thick, durable rock-like body armor shields Gravios from intense volcanic heat. Gravios' major organs are in the center of its body to also avoid to much heat. Its shovel-like head assists when feeding on hard rocky surfaces. Inside the stomach of Gravios is a special bacteria that helps them process and digest minerals, allowing Gravios to get nutrients from the minerals. Its stout legs support its great weight and a thick, club-like tail helps balance the creature and is useful in self-defense. Gaps in the Gravios' underside expel a knockout gas, potent enough to put many monsters to sleep, that is produced inside the Gravios' body. This gas is usually expelled after a Gravios has had a meal and used for protection against predators. Gravios can also expel flammable gas to cool themselves down and burn enemies. Since the Gravios feeds on rocks and minerals, they fuel their heat beams mainly with explosive ores. Gravios can are able to submerge themselves and "swim" through lava channels with ease due to their size and heavily-armored shell.
There are rare individuals that appear older, as the spikes on their body and tail are longer and more developed. They also have a more developed flame sac able to create a beam at high speeds, which they use to sweep away intruders. It also makes full use of its longer spikes on its tail by using a new tail swinging technique unused by other Gravios to attempt to kill intruders or attackers.
Relatively docile until provoked but like most wyverns are fiercely territorial. It is surprisingly passive to most other inhabitants of this area but considering its near-impervious shell, it is probably just not bothered by it except during its battle an Akantor. It has been discovered as proud and strong as they are some Gravios can be tamed and are used as pets by a few hunters.