This video is inspired by the chord progression found in the verse of Hotel California. It starts out in the key of Em. 
So, it starts out in Em, then goes to D major, and then to C major, and then pivots back to Em. It does this over and over. 
How does one work with that in an improvisation?
Here are some ideas to start with.
Hal Stead
https://youtu.be/U_6sU-2oIDw