Rufus Caligula is a red variant of Caligula that was introduced in GE2. It attacks relentlessly with both its boosters' blades and its icy roar.
The following information is taken from the official in-game descriptions of the Aragami found in the NORN Terminal's database.
God Eater 2 Rage Burst
After a "Red Caligula" was spotted at the Glasgow Branch and eliminated in the on the Far East land, it was reclaimed and classified, like all Aragami
Moves just like a normal Caligula, but attacks faster andcould prove difficult, even for seasoned God Eaters. Destroy the blades on both of its arms first, then focus on weakening it.
ATK Element: Freeze
Weaknesses: Blaze, Spark
Rufus Caligula is a red Caligula that appears in the story missions concerning Gilbert and Haruomi's past at the Glasglow Branch with Kate Laurie, Haruomi's lover. The Rufus Caligula has Kate's God Arc stuck on its back as a result of battle. Rufus Caligula first appeared at the Glasgow Branch and engaged in combat against Gilbert and Kate. It escaped by flight and left Kate's God Arc armlet damaged in the encounter which led to an infection of her Oracle cells through her body. Gilbert, who was fighting alongside Kate, was forced to kill and devour her body to prevent further incident from occurring (like the Corrosive Hannibal case). This incident caused Gilbert to be infamously nicknamed "Fragging Gil". When Rufus Caligula reappears near the Far East Branch, the Protagonist, Gilbert, and Haruomi hunt it down, awakening Gilbert's Power of Blood at the same time.
Rufus Caligula has its exclusive battle music titled after itself. This BGM is only used this once in the game's story and is not selectable for Free missions (However, it is selectable in the Archives).
It differs from a normal Caligula only by color in its respective story mission and cannot be devoured for materials.
The Rufus Caligula can only be fought again in its undamaged version in DLC Survival Missions after updating GE2 to version 1.4, where it gets a boost in speed to its movement as well as its attacks (though it remains slower than the Blitz Hannibal), as well as a modified charged flying attack. Some other changes are its more vulnerable hind legs, new attack while enraged, a greater circumference of the Ice Breath attack, and a greater weakness to Blaze than to Spark. Despite being slower than the Blitz Hannibal, it retains the wide-ranged attacks of its origin Aragami, arguably making it much harder than the supposedly extremely difficult Blitz Hannibal. If especially unfortunate, one single attack can lead to a full party wipe.