Translation help

Beorn is a shapeshifter, I think Tolkien uses that term to describe him. But I want to say it as describing someone who shapeshifts as “they are in their second form” I’m not sure if I want it to mean a second physical form or spiritual form (maybe a projection of themselves somehow or a gift) prob more physical form. As if I’m describing when Elwing changed into the bird with Earendil. I want to imply it was a gift give . I can’t remember if Ulmo gave her that ability as a gift, if it was permanent or what, but the idea that she went from her first form given (human form) then her second form (gift) being a bird. I totally understand if what I’m asking doesn’t make sense, lol, 😝. I want a word to use other than shapeshifter to describe someone who changes form as them being in their “second form”. You language wizards amaze me, I love tolkiens languages but can’t begin to figure out how to structure or use them, thanks for taking the time to read these and respond.

Well in Sindarin i-thadui gant would be "the second shape". Maybe as a compound Seinechad (New Form) or Seingant (New Shape), or even Adugant (Double Shape)? Others may have different ideas.