From the update:
Eternal Wardens are massive elite warriors clad in powerful armor spawned by the comet god to hold back the rift daemon’s invasion. Their units are strong and durable making for a great beginner’s army.
Havoc Brother Disciples are 4 small armies, each devoted to a specific havoc god. They all come with unique units as well as allowing you to upgrade your regular havoc brothers to fit in with the havoc god’s theme.