​The Sigma AU is an expansive, character-driven science fiction universe developed by Zoey K. Lavender and hosted on her blog, Zoey's Blog. Set in a future shaped by cybernetic enhancements, transhumanism, and geopolitical upheaval, with a strong focus on identity and LGBTQIA+ characters, the narrative unfolds through multiple interwoven arcs centered on characters like Zoey Lavender, Etrius vanRandr, and Taylor Wolfe.​

The universe is meticulously structured, featuring detailed character sheets, chronological short stories, and comprehensive worldbuilding entries. Key settings include Sigma City, St. Petersburg, and Berlin, each contributing to the rich backdrop of the series. The blog also delves into aspects like military vehicles, weaponry, and cybernetic technology, enhancing the depth of the world.