True Dragon

True Dragons are the highest spiritual beings, and are considered the strongest existence in the world, far superior to both a True Demon Lord and a True Hero.

They are beings "perfect as one", existing as the most complete spiritual life forms. They have no attachment to their physical bodies, only take those forms to respond to the desires of religions or similar (and also for convenience).

Birth
True Dragons are immortal and unblemished beings made of pure energy and formed by sentient beings’ prayers. They are basically god-like beings that represent and embody some aspect of nature.

After a True Dragon is born for the first time, it can never be truly killed. Even if the individual itself is killed, another True Dragon of the same natural characteristic will be born anew somewhere else. That new True Dragon will have the memories of the previous but will lose some aspects of its personality, while simply understand its nature of existence right after birth.

Relationship
Although the True Dragons refer to each other as "brother" or "sister", they are not blood-related in the biological sense.

"Star King Dragon" Veldanava
The greatest of the True Dragons and the strongest among them. He is also the God that created the world in which they live. The husband of Lucia and father to Demon Lord Milim Nava.

"White Ice Dragon" Velzard
Partner of Guy Crimson, Velzard is known to be second in birth as well as in power from Veldanava. She is prideful and haughty, and was incredibly jealous when Veldanava granted Guy important roles instead of paying attention to her.

"Scorch Dragon" Velgrynd
Partner of Rudra Nam Ul Nasca, Velgrynd is the fastest Dragon in existence. Her very essence is that of 'acceleration' and 'high momentum'. Although slightly hot-headed, she is very compassionate, especially to her allies and family.

"Storm Dragon" Veldora
The youngest of the True Dragons. He is connected with Rimuru by an agreement and was known to frequently rampage here and there, therefore gaining the reputation of "the Evil Dragon" spread by Luminism. Known to act very childish.

Milim Nava
A Dragonoid, she is one of the oldest and strongest Demon Lords. The daughter of Veldanava and Lucia, she inherited the greater part of her father's power resulting in many comparing or even considering her a True Dragon.

Gaia
As an offshoot of Veldanava's power and as his potential vessel for reincarnation, Gaia is essentially a lesser version of the True Dragon species physically, and is comparable to them in terms of power. In the 13.5 Databook, his race is even listed as "True Dragon".

Charybdis
Similar to Gaia, Charybdis is an offshoot of a True Dragon's power (Veldora), and inherits similar qualities such as the extremely large size and the ability to resurrect elsewhere, even after complete destruction. Charybdis's official race is "Dragon" (the same kanji used for True Dragons 竜)

Trivia

 * In the first databook, Milim is mislabeled as one of the 4 True Dragons.