The wait's always worth it for me here. ;-) His reactions were fantastic and quite believable! And enjoyable to read. Though, I got the vibe you maybe thought the creatures were huge? Could be wrong, but I better specified their size this post just in case. Heh. Sorry! 

With the success of the shield, Ghent would feel the impact of the monster with it. Wouldn’t be pleasant, but wouldn’t be completely debilitating. The shield will also be drawing on his own strength and willpower, as well on the world's magic. How much of his strength something like that saps/utilizes would depend on how well he can tame the magic. The greater his connection with magic, the heavier the burden it'll take before drawing on him in place of its own energy.

The sensation of the world's magic would fluctuate with his willpower and focus, too, and its strength will, of course, react to his emotions and overall focus on it. So, the shield could shatter from the one hit, or hold up for another. What happens there is entirely up to you, since you know him best! If you feel like he could maintain it longer than the single hit, have at it!

You're most welcome! Always glad to answer questions.