Yourself

This enters as a copy of target non-artifact creature except it is Blue/Black and no other colors, is a Legendary Changeling and no other creature types, and has +1/+1 and the following:

While this is untapped, the copied creature is goaded and must attack you.

Whenever this blocks and whenever this is destroyed, all permanents on the battlefield lose all colors and become Blue, then place a -1/-1 counter on all Blue creatures.