Sub-Variant Werewolf

Rex has already determined that he would turn Giana and Prof. K at the moment he heard that the two are inside the Supernatural territory searching for him, he has his mind fixed on a plan that came to him from nowhere.

'I only wanted to turn Giana to make her understand, but she can't survive on her own'

As she was stripped away from her ninth-rank realm powers, degrading from the pillar of humanity with dual elements into nothing more than a measly superhuman, she has become incapable of surviving alone.

Going through the Humming Damned Forest is an impossibility for her now.

Not to mention, the Great Barricade is miles and miles away from the castle. If she can't reach the end of the Humming Damnef Forest, then reaching the Great Barricade is a complete pipe dream.

Thus, his decision to involve Prof. K is the best way to resolve those issues.