In the Hindu religion, Maya is centered around the concept of "illusion" and has multiple meanings. In fact, Maya's very name is "illusion" in Sanskrit. She manifests, perpetuates and governs illusion as well as the dream of duality in the universe.
"The Hindu personification of Illusion. It is said to have the power to make humans aware and become enlightened about "phenomena" caused by things on earth. A Maya of Burmese lore was a mother goddess and may have some relation to the goddess of illusion."
—Shin Megami Tensei: Strange Journey Compendium.
Maya serves as the Sector Boss of Sector Grus. It was her power that twisted Grus' landscape to its warped form; she also threatens Zelenin and the protagonist with her vicious illusions until the protagonist encounters Commander Gore and makes him awakens to the true power of the Ubergestalt. As a result, the two musters enough strength to cast them away.
Upon breach of her sanctum, a twisted blend of the first four sectors, she appears, sarcastically asking whether the protagonist's repeated defeat of the Mothers was some form of entertainment, and if the protagonist had enjoyed the act of "matricide" so much she was next in line.
Upon defeat, she claims that she is too a child of Mem Aleph and then drops her Exotic Matter. Maya can then onwards be produced from a special fusion of Hariti, Succubus, Incubus, and Airavata.
The battle against her can be dangerous for a party specialized in spellcasting, as her own special skills allow her to negate any form of offensive magic and instantly kill the offender. As befits the goddess of illusions, she can also cast Illusion Ritual, buffing her evasion stats. She is weak to Bullet damage, but repeated castings of Illusion Ritual will allow her to dodge most attacks.
Other than that, she knows strong elemental magic (-dyne spells, Gate spells) and Ultraviolence, an exceedingly strong Physical attack that will hit the entire party, and Evil Vortex, a damaging attack that can inflict Stone status. Dekunda is also in her repertoire.