Agnus is the chief technological researcher and alchemist of the Holy Knights and develops demon-eradicating weapons for the group. Agnus seems to be introverted and a workaholic, rarely showing up in any event. Because of this, only few people in the cult know of him. Later, it is discovered that he has been experimenting with the broken Yamato (which belonged to Dante's late brother Vergil) and creating demon-based weapons. During times of stress, he speaks with a pronounced and noticeable stutter. He bears a slight resemblance to Arkham, although it is unlikely they are related.
Agnus is seen in the game clashing with Credo, Supreme General of the Holy Knights. However, he is extremely obedient to Sanctus, the Order's leader, obeying his commands and never questioning Sanctus' will. He speaks to Sanctus with a respectful and obsequious, sometimes even flattering, tone. According to Agnus's dialogue with Dante, he has misanthropic views, criticizing the stubbornness and foolishness of human nature. He is voiced by T.J. Storm.
Agnus Angelo Edit
Agnus also possesses an alternate form, Agnus Angelo, resembling a cross between a beetle and a moth. In this form, he can summon a burst of deadly fireballs and drain the player character's health points to replenish his own vitality.
The Gladius is an artificial demon created by Agnus through magically cross-breeding a sword with a reptile. It is capable of flight, and can transform its entire body into a bladed weapon able to be wielded by others. If damaged, it will drop to the ground in its weapon form, where it can be picked up and thrown at a locked-on enemy using Nero's Buster. Agnus wields them both in his human and Agnus Angelo forms, and his own Buster moment involves being impaled with the demons.
The Cutlass is an artificial demon created by Agnus through magically cross-breeding a sword and a fish. Its dorsal fin, an incredibly sharp blade, allows it to cut through earth, stone, and metal, effectively allowing it to swim through solid land. They attack by diving out of the ceiling or floor, but if damaged they will remain knocked out on the floor. Agnus wields a Cutlass in his Agnus Angelo form.
The Basilisk is an artificial demon created by Agnus through magically cross-breeding a gun and a dog. It is able to fire its fiery skull from its body like a bullet, and then regenerate a new one. Agnus is able to summon six Basilisks at a time and use them as an army while in his Agnus Angelo form.