Charybdis

Charybdis (暴風大妖渦) is a gigantic one-eyed mindless blood-thirsty calamity-class Monster, heralded as the Ruler of the Skies. Born from a cloud of Veldora's Magicules, it can be said to be part of Veldora's "family," similar to Rimuru as it is also called to be Veldora's child. As it has no solid sense of self, it operates solely to satisfy its lust for destruction.

Since it is a spiritual life-form it lacks a physical body and thus requires a host for the sake of survival. It is also strongly resistant to magic attacks due to its extra skill "Magic Jamming." As it is originally from the spirit world, it is also accompanied by a couple of Megalodons who are strongly resistant to magic attacks as well. Though Charybdis is said to be a Calamity-class monster, in reality, it is no weaker than a Disaster-class monster (i.e., at the level of a long-time established Demon Lord Seed) since it wields a fraction of Veldora's power. The only reason it hasn't been considered as one is due to its inability of rational thought.

Background
Born from the malice and violence of Humans, Charybdis entered a cycle of spreading widespread destruction and death to whatever caught its interest, before being subdued and killed, and eventually resurrecting a few centuries later. Seeking to end the cycle, the Hero sealed Charybdis away inside a dimensional barrier hidden in a cave somewhere in the forest of Jura, with its location being only known to the Hero and the Dryads.

Demon Lord Attack Arc
Moderate Harlequin Alliance members Footman and Tear, under directions from the Demon Lord Clayman, tricked Phobio into becoming the host for Charybdis so that it could inherit his hunger for revenge against the Demon Lord Milim. In the process, the dead dragons supplied by the Majins became additional 13 flying armored sharks that accompany the colossal monster.

Treyni, Trya, and their sister dryad of the Jura Tempest Federation had attempted to stop Charybdis as soon as it entered the Jura Forest but were forced to retreat temporarily due to the immense power and magic jamming abilities of Charybdis. Rimuru Tempest was summoned to respond to the threat, and he decided on an all-out attack on Charybdis by every squad that Tempest has. Additional forces from Dwargon also arrive because Gazel considers it a dangerous situation even for Dwargon, as well as to help out his "junior as both king and Hakurou's student," Rimuru. Milim was left out of the fight on Rimuru's orders, despite her wanting to destroy it herself and her capability to do so.

In the ensuing counterattack, all of the flying sharks were killed via physical attacks, and Charybdis was then attacked directly. However, its magic jamming, ultra-regeneration, and scale swarm attacks made the fight near-impossible to win for the allied forces in that particular interception attack because, as Rimuru later notices, the allied forces didn't use the correct attack methods. Charybdis then mentioned Milim, as the target of its vengeance, which convinced Rimuru to let Milim destroy its physical body but let Phobio's host body out unharmed. Rimuru then extracted Charybdis' magicore from Phobio and isolated it in his stomach. It was Charybdis' assault on Tempest and Milim's deductions that led to Rimuru to see Clayman, as well as the other members of the Moderate Harlequin Alliance as an enemy, and Carrion as innocent.

The Octagram Soars Brightly Arc
As a failsafe against betrayal, Demon Lord Clayman prepared a trap for his subordinate Yamza. The moment Yamza truly intends to betray Clayman, a Charybdis-Fragment that Clayman secretly planted onto Yamza gets activated and consumes Yamza. During the war between the Tempest-Yuurazania Allied Forces against Clayman's army, Yamza who intended to surrender and leave Clayman's forces after divulging all information to the enemy, caused the trap to be activated and Yamza was consumed by the Charybdis-Fragment which created an imperfect temporary incarnation of Charybdis from Yamza and the war's surrounding corpses. This Charybdis would eventually scatter because it lacked the core, which was still sealed within Rimuru's stomach. However even in it's temporary form, it still had enough power to cause a lot of death during the chaos of the war, attacks even by Calamity-class fighters like Albis being completely useless. But before Charybdis could cause any damage, Benimaru exterminated it, proving that Benimaru himself had reached Disaster-class.

Hero Awakening Arc
In order to get Ifrit out of Rimuru's stomach so that he may serve as Veldora's personal secretary, Veldora requests Rimuru to free him. In order to do so, Rimuru grants Ifrit the sealed core of Charybdis as his new body, while Veldora grants Ifrit the name Charys.

Abilities
Special Skills:
 * Tempest Scales
 * Laser Look

Extra Skills:
 * Gravity Manipulation
 * Magic Sense
 * Magic Jamming
 * Ultraspeed Regeneration

Tolerance:
 * Cancel Pain
 * Resist Melee Attack
 * Resist Paralysis

Trivia

 * Since Charybdis needs a carrier to manifest, it is unknown which were the previous Charybdis recipient/hosts before Phobio.
 * The name Charybdis comes from a sea monster in Greek and Italian myth.
 * Charybdis in all technicalities can be considered as something akin to that of an older sibling to Rimuru Tempest due to him having also been born from the excessive Megicules excreted by Storm Dragon Veldora.