ꭁ

Design
Apparently $⟨ᴔ⟩$ with a slash through the o, but because this character only occurred in italic, it's not clear that it isn't $⟨ꜵ⟩$ with a slash.

Derivatives

 * ꭂ

Usage notes
The Teuthonista front rounded vowels, from high/close to low/open, are:
 * y ꭚ ø ꬿ ꭁ ⱥ