he possessed junghyuk body for a moment
Some clarifications of his skill
Yep more like, his skill in a way allows himself to see the world in the eyes of the protagonist (the protagonist being Yoo Jonghyuk)
No he didn't become Yoo Jonghyuk or steal his body or anything,the one controlling the body is still the protagonist and Dokja is more like sitting on the protagonist's head,seeing through his eyes and feeling the way Yoo Jonghyuk moves and the way he holds his sword and etc.
Once he experiences this viewpoint he is given the option to use one of the protagonist's skill in this case he chose Cold Resistance
DID HE SUDDENLY TRANSFER HIS SOUL INTO THE HANDSOME MC's body?!?!