Maggie Lacivi is a former classmate and friend of Ava Ire. She is pacted with the demon Tuls Tenebrose. She has powerful plant-like abilities and can make her appendages morph into strong, tree-like vines.

Maggie is short for Magnolia, a type of flower. "Lacivi" is a variation of the word "lascivious" which means "flirty" or "lustful". Apt, since her associated sin is lust.

Maggie is rude, confrontational, egotistical, and downright hostile. However, Ava mentions that she wasn't always this way; something that happened between them in the past harshly changed her personality. They both blame Ava for whatever happened, and Maggie has hated her ever since. However, Maggie keeps a small photograph of her and Ava as children in the cabinet embedded in her stomach, implying that she may still care for her former friend deep down. 

In spite of her hostile personality traits, Maggie falls in love very quickly and develops a crush on Gil Marverdealmost at first sight, calling him her "prince". As he is the sixth person she's developed such a crush on, it can be surmised that she is somewhat emotionally immature and cannot restrain her emotions. She even forces Tuls to use his magic to create a special flower that will help the object of her affections "uncover the desire to be her significant other".

Although Maggie has formed a pact with Tuls, she is thoroughly unconcerned about what he wants and seems only to care about what she can get with his power. She deliberately and carelessly harms his creations, constantly belittles him, and has ignored his desire to reunite with his beloved Ranunculae for four years. This carelessness may be because she is not fully aware of what will happen if the pact fails, perhaps because she is unable to take things as seriously as she should.

Lust, the sin of deep obsession, is associated with Maggie which is reflected in her near-instant flirty attitude towards Gil and her desire to be loved in return. Maggie's clingy tendencies can be interpreted as a stigma of depression and abandonment.

The pupil shape chosen for Maggie is a triangle to represent her sharpness, providing contrast for Ava, whose pupil is a circle. Michelle describes this "....as if [Maggie] is striving to become everything Ava could not; the sharpest shape against the softest."