The Apostle Paul on his visit to Athens saw shrines erected to many gods. Just in case they missed one, they had one to “The Unknown god.”
Today’s unknown God may be the Holy Spirit. We know about God the Father, who created the world and holds it in his hands. We know God the Son, who came, lived, died, arose and ascended to the right hand of the Father to intercede for us.
But I fear the average Christian knows little about the Holy Spirit.
The Bible has the Holy Spirit as co-equal with God the Father and God the Son.