Depends on how we want to read it.
Odyn has 2 ravens associated with his Havi persona/disguise. Have we ever seen ravens associated with normal titanic form?
Medivh is adorned with raven feathers, a raven staff, and shapeshifts/polymorphs into a raven.
Both are strong candidates. We havent seen Medivh for s while but hes still active. Odyn could quite easily go big baby rage Prime Designate and do something that initiates that whisper/prophecy.