Dagruel, known by the epithet the Earthquake, is a prominent figure among the Demon Lords in the series. He is a member of the Octagram, the ruling council of the most powerful Demon Lords, and is recognized as one of the ancient second-generation Demon Lords. He is a giant, a member of the Giant Tribe, and possesses a colossal physique that towers over most other beings, often appearing as a large, muscular man with blue hair slicked back and three distinctive teardrop tattoos on his face.

His origins lie in the mythical age when an evil giant, born from the depths of the earth, was defeated by the supreme being Veldanava. This entity was split into three separate entities, with Dagruel being one of them. Unlike his wicked brother Fenn, who was sealed away, Dagruel and his other brother, Glassord, renounced their malevolent past and sought redemption. As a reward for his change of heart, Veldanava granted Dagruel a parcel of land and entrusted him with the solemn duty of guarding the Heaven Tower, a role that has shaped much of his long existence.

Throughout his long life, Dagruel has formed several key relationships that define him. He is a long-time rival and sparring partner of the Storm Dragon Veldora Tempest, with whom he has fought many times, and their battles have always ended in draws, earning them a deep mutual respect. Despite the destructive nature of their clashes, this rivalry is not born of malice but of recognition of equal power. He also shares a close friendship with Dino, the Fallen Demon Lord, having generously provided him with accommodation for centuries. His relationship with Luminous Valentine, the Vampire Demon Lord, is far more complex. They were once close through his friendship with her creator, Twilight Valentine, but after Twilight's death at Luminous's hands, their relationship soured into a fierce and prolonged power struggle over territorial boundaries.

Dagruel is also a father to three sons: Dagura, Liura, and Debura. Tragically, his wife Kisara died while giving birth to them, a loss that brought him great devastation. As a father, he demonstrates a pragmatic and deeply concerned nature. Recognizing his sons' recklessness and relative weakness, he arranged for them to travel to the nation of Tempest to train under Rimuru, accurately predicting that the slime's merciful nature would ensure their safety. This act shows he is not only a strategic thinker but also a parent who cares for his children's development.

In terms of personality, Dagruel defies the typical brutish image of a giant. While he exudes quiet confidence in his overwhelming strength, he is composed, dignified, and possesses keen observational skills. He is astutely aware of the deceit and political maneuvering common among his fellow Demon Lords and holds a deep-seated disdain for betrayal, as shown by his outrage at Clayman's treachery. Though he is a formidable warrior, he is not aggressive without reason and respects power in others when it is earned. His motivations are largely tied to the protection and prosperity of his territory, the Barren Lands. This region was devastated centuries ago during a battle between Milim Nava and Guy Crimson, which turned it into a deadly desert. A significant portion of his efforts is dedicated to mitigating the damage from this catastrophe and slowing the progression of desertification, which also fuels his desire for Luminous Valentine's more fertile lands.

Dagruel's role in the story is initially as one of the powerful, established Demon Lords on the council. However, his significance grows during the great conflict with the angels. In a pivotal turn, he betrays Rimuru and leads his giants in an assault on the Holy Empire of Ruberios, fighting against Luminous Valentine and her allies from Tempest. During this battle, he proves to be an almost unstoppable force, easily overwhelming powerful characters like Luminous and Shion. His power is so immense that even Shion's evolved abilities could not deliver a decisive blow. The conflict culminates in a final, epic duel against his old rival, Veldora Tempest, where he fuses with his two brothers to achieve his ultimate form, Ashura, but is ultimately defeated.

Following his defeat, Dagruel undergoes a significant development. Upon learning the true nature of the angelic threat, he realizes his mistakes and seeks redemption. He willingly sacrifices his own energy to restore fertility to his ravaged land, finally achieving his long-held goal of healing the Barren Lands. He then entrusts the future of his people to his sons, stepping away from his role as their direct ruler.

As a combatant, Dagruel is among the most powerful beings in the world, with a magical power rivaling that of the True Dragons. His abilities transcend both magical and physical realms. He possesses Intrinsic Skills such as Magic Nullification, which automatically neutralizes all magic attacks, and Seismic Waves, which allows him to create devastating tremors and lightning strikes. Despite lacking an Ultimate Skill, his raw power as a spiritual lifeform is immense. His signature techniques include Tidal Wave, a large-scale destructive attack, and Quasar Break, a technique that creates a pseudo-black hole to absorb and destroy all matter. He is also capable of moving within a stopped time, a feat that places him at the very pinnacle of combat prowess in his world.