The changelings are trying to reach peace and equality with the other races. But they are parasites. Even if peace can be accomplished relatively quickly, equality will take much, much longer. Additionally, there is a huge crisis which demands cooperation quickly.

This crisis is not from another species, but from the physical manifestation of the elder ruler of Equestra.

The sun.

(Tags may be added or removed later. Rated Teen for some more intense subjects, such as historic wars, prejudice, and possibly some darker themes later. ABSOLUTELY no clop, and almost certainly no gore. Would get a science-fiction genre, but that's not an option.)