Chibi Shadow Sonic "Midnight-Up!" is a brand new "Imagine It!" Sticker, you can receive the sticker as a reward by putting a charged sticker on my post.

The frame features the Characters' faction.
In case of Shadow Sonic "Midnight-Up!", he belongs to Nefarious Empire.
The Leader of this Evil Fraction is Dr. Golden "Prepare-Up!".
And both Shadow Sonic "Midnight-Up!" and Dr. Golden "Prepare-Up!" are responsible of mind controlling poor Origin Sonic "Midday-Up!"

Since Shadow Sonic "Midnight-Up!" is as well related to fangame "Aureate Afterglow!!" the post is on the gamepage as well.

Some references related to Shadow Sonic "Midnight-Up!" appearance and "AA!!" fangame:

Shadowed Dr. Eggman Anomaly, with yellow glow (Eyes and mouth)

Aureate (golden) in this case moon, while in fangame there's Aureate sun
(moon and sun have a connection of golden/yellow, not only in color, but also in impact)

Shadow Sonic "Midnight-Up!" represent himself as the "Gold Crescent Moon",
while Dr. Golden "Prepare-Up!" represent himself as the "Gold Crescent Sun"
and Origin Sonic "Midday-Up!" represent himself as the "Gold Sun".
I'll get to this at some point. Now I can tell this secret for now.