A full ref I made for a friend for their Drift Wing(?) character, who is obviously very heavily based off of Bill Cipher, of course there's some new features added to said character after I introduced them to Rift Wings that just really fits to their Bill :)
This was also one of the very first Drift Wings I gave away-they gotten it for free because they're a good friend, but also because their Drift Wing is heavily reference/based on a copyrighted character.

Drift Wings and Rift Wings are Closed Species that belong to me
Bill Cipher and Gravity Falls is © Alex Hirsch and Disney