After the magic barrier broke, the magic beast leaped toward the princess as it slashed its claws at her, but Allen didn't allow such a thing to happen, especially when he needed that princess alive, or else how could she vouch for his identity?
With that in mind, Allen used his <Supreme Mage> talent to cast a paralysis magic spell towards the magic beast, and before its body could fall to the ground, Allen used his mana to keep the magic beast in the air.
With those actions Allen took, it was like he froze the magic beast in place and it could even be mistaken for Allen using time magic to stop the time around the magic beast. That was how great Allen's mana control was.