The Isu are the fictional precursor species in Assassin's Creed, including Minerva and Juno.
The Isu are an advanced civilization that existed before recorded human history in the series' mythology. They created humans and developed powerful artifacts, including the Pieces of Eden. Their civilization was devastated by a catastrophic solar event, after which humans inherited a world shaped by Isu technology and conflict.
Minerva, Juno, and Jupiter are prominent Isu figures encountered through messages, visions, and ancient records. Their legacy connects the modern-day plot to the historical stories experienced through the Animus. The series gradually reveals their role rather than presenting all of the information at once.
“First Civilization” is another term used for the Isu, which makes it a tempting answer, but the question asks for the species' name. Templars are a human organization, not the precursor civilization. The spelling “Isu” is the concise canonical term used in the games and reference material.