Talk:Shadow Play - Part 2/@comment-1031724-20171001054935

Suppose Starswirl and the other Legends know about something else that's like the Elements of Harmony, they weren't able to use its full power and had to seal themselves away along with the Pony of Shadows (think how Celestia could only banish Nightmare Moon, not purify her), but the Mane 6 can use its full power and use it to defeat the Pony of Shadows without a sacrifice.

That would explain why Chrysalis is targeting the Mane 6 instead of Starlight in the Season 8 premier...