The Argonaut Leader was Jason, a 5-letter name. He was accompanied by Idas, a 4-letter name, and Heracles, an 8-letter name. Jason was the leader of the Argonauts, a band of heroes in Greek mythology who set out on a quest to retrieve the Golden Fleece. Idas was a brave warrior and Heracles was a demigod known for his strength and courage. Together, they formed a formidable team that was able to complete their mission.