Clairestiel
Clairestiel is the mashup nickname used in fandom to refer to Castiel while possessing Claire Novak as a vessel, as he does in the episode 4.20 The Rapture.
When Jimmy Novak, Castiel's usual vessel, is held captive and his wife (and Claire's mother) Amelia is possessed by a demon, Castiel takes Claire as a vessel and expels at least two demons from their hosts. Castiel then tells a dying Jimmy Novak that the ability to be an angelic vessel is in Claire's blood, as it is in Jimmy's, and assures Jimmy that he has Heaven's gratitude for his service. However, rather than accepting his chance for peace in Heaven, Jimmy begs Castiel to take him back as a vessel as he wants to spare his daughter the suffering that he's experienced. Reluctantly, Castiel agrees to Jimmy's request, releases Claire, and returns to using Jimmy as his vessel.
