Thoth's mythological roles are extensive and interconnected. As god of wisdom, he was believed to possess knowledge of magic and secrets unavailable to the other gods - a mastery of heka (divine magic) that made him the ultimate arbiter of disputes among the deities. In the conflict between Horus and Set, Thoth frequently served as mediator and judge, using his impartial wisdom to resolve conflicts that threatened the stability of the divine order. His association with the moon made him the natural counterpart to the sun god Ra: while Ra illuminated the day, Thoth's moon watched over the night; while Ra traveled through the underworld during the hours of darkness, Thoth assisted in the nightly battle against Apep, the serpent of chaos, helping to ensure the sun's rebirth each dawn. The phases of the moon, precisely measurable and cyclically regular, made Thoth the god of time and calendars; he was credited with inventing the Egyptian civil calendar of 365 days, divided into twelve months of thirty days plus five intercalary days - a system so effective that it remained in use for millennia.

Thoth's most visually dramatic role is his function in the Weighing of the Heart, the central judgement of the Egyptian afterlife. In the Hall of Maat, before the divine tribunal presided over by Osiris, the heart of the deceased was placed upon one pan of a great balance scale, while the ostrich feather of Maat was set upon the other. Anubis, the jackal-headed god, knelt to operate and verify the balance; Thoth stood beside him, writing palette and reed pen in hand, ready to inscribe the result. As the god of precise measurement, accurate record-keeping, and unerring truth, Thoth was the only being capable of documenting this moment with the absolute accuracy that cosmic justice demanded. His recording was not merely administrative but performative - the act of writing the verdict made it permanent and irreversible, establishing the deceased's fate for all eternity. If the heart balanced the feather, Thoth recorded that the soul was m3-heru ("true of voice"), justified before the gods. If the heart was heavy with wrongdoing, Thoth's record condemned the soul to annihilation by Ammit, the Devourer of the Dead.

As the inventor of writing, Thoth occupies a position of unique cultural importance. Egyptian tradition credited him with creating mdw-nTr - literally "the words of the god" - the hieroglyphic script that combined logographic and phonetic elements to produce one of the world's most visually striking and theologically significant writing systems. All forms of knowledge were understood to derive ultimately from Thoth: mathematics, astronomy, medicine, law, philosophy, and the magical arts. The Book of Thoth, a legendary text said to contain all the hidden knowledge of the universe, was believed to have been written by Thoth himself and hidden away for those worthy of its secrets. This mythological text - which no mortal was believed to have fully mastered - became one of the foundational legends of Western esotericism, influencing alchemical, hermetic, and magical traditions for two millennia.

Thoth's relationships within the divine family reflect his multifaceted nature. He was closely linked to Maat, the goddess of truth and cosmic order - so closely that the two were sometimes understood as husband and wife, their union representing the perfect harmony of wisdom and justice. He was also associated with Seshat, the goddess of writing, architecture, and measurement, who served as his female counterpart and collaborator in the preservation of knowledge. In the Heliopolitan creation myth, Thoth assists Ra in making the universe by serving as the sun god's voice: Ra conceives the world in his mind, but Thoth gives words to Ra's thoughts, bringing creation from potentiality into actuality. This role as the divine voice - the mediator between divine intention and manifest reality - parallels his role as the scribe who records the judgements of the afterlife.