What was the sixth nation that was added to Iroquois confederacy?

The sixth nation added to the Iroquois Confederacy, also known as the Haudenosaunee, was the Tuscarora. They joined the Confederacy in the early 18th century, around 1715, after migrating northward from their original territory in North Carolina due to conflicts with European settlers. Their inclusion helped to strengthen the Confederacy and expand its influence in the region.