Having the beast so close is something Klaus already knew. He is the one who is in control of this place, as he carefully observed the whole place just before throwing all that flour around. That's why he wasn't surprised.
He took a step back to gather momentum, recharged his arm with a powerful positive energy, and bent his body. In doing so, he dodged the first attack of the cursed beast, which was extremely angry and had strange knives in its hands.
From its body, it gave off a strange aura that stirred Klaus' emotions and feelings, wanting to anger him. That meant it was a beast of Anger.
Each type of beast has its specialty, which does not necessarily have anything to do with the Calamity that gave birth to them. In this case, one of the specialties that the cursed beasts of Anger (or Wrath) tend to enjoy is great melee skills.
Klaus knew this, so keeping this thing away from him was necessary.
