What are principalities as mentioned in sealings?
To my knowledge, neither the Lord nor his servants have elaborated on this issue. That means the path of discovery is open to us! Here is one way to go about finding that answer. Here is Gramps’ Guide to Finding Gospel Answers.
First, look up the definition. I’ll help you with this one. It means “ruled by a Prince.” Hmmm, I wonder what the Lord is implying here. Prayerfully ponder that. Could you be a Prince? What kind of Prince would God want you to be? If you are the Prince, who is the King? If that helps, great. If not keep praying and go to step two.
Second, look it up in the scriptures. By my count it is mentioned 15 times, so that won’t take too long. If that helps, great. If not keep praying and go to step three.
Third, search LDS.org. See if anyone has spoken about it. If that helps, great. If not keep praying and go to step four.
Fourth: Check other resources such as Strong’s Concordance, the Blue Letter Bible, Webster’s Dictionary 1828, and the Online Etymology Dictionary. If that helps — great! If not, keep praying and go to Step five.
Fifth, get on your knees and explain to Father that you have done everything you can do to answer this. Ask Him if He will help. Sometimes He will, other questions just have to wait.
Sixth, if you don’t have the answer yet, keep it in the back of your mind. Some things take time. Begin the steps again with a new question. Perhaps the new question will give you insights to this one.