Double’s reference is the Trinity cult from the Skullgirls Game series Skullgirls is a 2D fighting game developed by Reverge Labs and published by Autumn Games. In Skullgirls, players engage in combat against one another with teams of one, two, or three characters, attempting to knock out their opponents or have the most cumulative health when time runs out. The setting of the game revolves around the "Skull Heart", an artifact that grants wishes to women. If a wisher with an impure soul uses the Skull Heart, she is transformed into the next "Skullgirl", a monster bent on destruction. Double (ダブル) is a monstrous, transforming creature working under the Trinity, responsible for ensuring that the Skull Heart falls into the "right" hands and manipulating events according to the goddesses' will. Her current guise is as a nun under the name Agatha Gloomfoil. The Trinity is a trio of goddesses in Skullgirls. They are Venus Lovelace, Aeon, and their mother. They have a church dedicated to them called the Grand Cathedral (which is also a fighting stage in the game). Many people come to the church to give their confessions, tithes, and so on. Because the Trinity are females, people will say "Goddess-speed" to anyone who could use luck. Parasoul and Double worship them with their Petran cross (inverted crucifix) necklaces (but the Trinity mostly uses inverted celtic crosses in their statues). Double calls them "masters".