
They often put things in terms of theater, referring to Angelina's death as the "falling of curtains" and comparing their conflicting Grim Reaper and demon relationship with Sebastian to the famous play, Romeo and Juliet. Grell is very fond of using double-entendres and incorporating plays into their speech.

However, due to how naturally impulsive Grell is, their adherence to the Grim Reaper rules remains questionable for example, on one occasion, Grell was about to slay Aleistor Chamber, ignoring Ronald's cry that killing humans is forbidden. But, after a period of suspension, Grell begins to respect the duties of a Grim Reaper, enough to preach the importance of soul reaping to Ronald Knox at one point. Grell was, at first, dismissive of the Grim Reaper principles-which include the necessity to be neutral in human affairs-as evidenced by their unlawful partnership with Angelina Dalles. They despise hesitation in their partners, and find that meaningless emotions serve as an impediment to one's goal. In Grell's personal view, human relations are not of great significance, and hence, they do not understand a human's reluctance to kill a person he or she cares about.

Grell is predisposed to resorting to violence in order to eliminate whoever annoys or hinders them, and has had numerous clashes with Sebastian in one instance, upon encountering Sebastian on Campania, Grell immediately expresses their intention to have a "death match" with him and proceeds to attack him. They are a ruthless, bloodthirsty individual who is even willing to kill their own comrades once they lose interest in them. They possess a strong predilection for the color red, and believe that substances which reflect that color, such as blood, can be used to achieve beauty. Grell is over-the-top, flamboyant, and outspoken-they once told Sebastian Michaelis their wish to do some "vigorous exercise" with him, despite the latter's repulsion.
