Anne of Abyssal Red allows Lucy to create an alternate space known as Anne's Chamber (アンの部屋, An no Heya?) upon activation within close to medium proximity, where Lucy's targets are transported to. The eponymous Anne is a giant doll-like creature with immense strength and speed, who is shown to chase targets mainly to capture them inside the chamber while playing hide-and-seek or tag. While inside this space, no attacks can penetrate nor affect Anne, including Nathaniel Hawthorne's blood bullets. However, Anne is not immune to restraining forces, such as John Steinbeck's grapevines.
The room contains an exit door, which can lead the targets brought to the dimension back to the real world. Apparently, leaving Anne's Chamber through the exit door will make the person's memories regarding everything that transpired inside vanish. However, Lucy can also link the door to another location of her choice, such as an aircraft's outer wall. Another door leads to the chamber's prison known as the secret room (緋文, himon?), which traps Lucy's unconscious captives held by various puppet hands or sometimes with the aid of Anne. It is supposedly impossible to escape through force once dragged inside the secret room. Lucy hints that the only way to open the door is through a key, but it instantly morphs into a malevolent being when someone attempts to use it; even Lucy admits that she does not know how to use the key. Thus far, the only way for the prisoners to be freed is through Lucy deactivating her ability.
Lucy has also used Anne of Abyssal Red for several purposes, one of which is hiding individuals like Yukichi Fukuzawa during the events of Cannibalism. She later uses this ability during the terrorism incident perpetrated by the Decay of Angels, which her team occasionally utilizes as their base of operations or when infiltrating enemy territory without being noticed or seen. During this time, Anne of Abyssal Red is capable of transporting Atsushi Nakajima and Kyōka Izumi while Lucy remains in the outside world. It is also possible to delay time inside Anne's Chamber, which can be used to prevent products like coffee beans from easily perishing.
The ability can be activated by Lucy anytime, albeit within close proximity and only on specific people she chooses to enter Anne's Chamber. As such, when she has to transport individuals beyond her literal reach, Lucy needs to approach the target to be closer to them through several means, such as diving on water to get nearer to a drowning target or jumping from the sky to approach a target suspended mid-air. Though Lucy only allows people she chooses to enter Anne's Chamber, external parties can also enter the space through connecting something to Lucy's chosen target. For example, Hawthorne was able to enter Anne's Chamber after attaching a thread of blood on Atsushi when Lucy transported him and herself to her dimension.
Anne of Abyssal Red is a reference to the real-life Lucy Maud Montgomery's novel Anne of Green Gables. It narrates the story of the protagonist named Anne Shirley, an orphaned, red-haired girl who was sent by mistake to two middle-aged siblings in a fictional town where a farm known as Green Gables is located.