THE VOICE
Go roundabout, Peer!
PEER
No, through! [Cuts and slashes.]
There he fell! [Tries to advance, but strikes against something.]
Ho ho, are there more here?
THE VOICE
The Boyg, Peer Gynt! the one only one.
It's the Boyg that's unwounded, and the Boyg that was hurt,
it's the Boyg that is dead, and the Boyg that's alive.

What is Bøyg or who is Böjgen? He is invisible and strong. You can not se him or beat him.
the Bøyg is a creature who has no real description. On the question "who are you?" The Bøyg answers: "myself".