Probably one of the top ten episode of the show and hands down one of the most important episode of Season Two.
Skeletor hatches a scheme to get inside Grayskull. All other attempts haven't succeeded. He-Man is there or Sorceress is there to stop him.
He sends Zoar into another dimension which leaves Grayskull unprotected.
Zoar sends a message to He-Man and Teela to protect the castle. Specifically, Teela is chosen out of nowhere to be the heir to Castle Grayskull.
Teela is baffled about the choice to do this as she knows nothing about doing that.
However, as we all know Teela is Sorceress's daughter, and she has an instinct to do the job.
This episode is what He-Man is all about. Animation is high quality, they addressed a story arc between Teela and Sorceress, and the action is great.
This is like a preview or training if you will to see how Teela, the next one to be Sorceress would
act in a situation of danger for Castle Grayskull.
There's a nice mother/daughter moment in the end.
The writers delivered a nice chapter into the series here.