Magnus tries to get his sword up to block him, since his shield is busy continuing with the momentum shift of his attempt to knock it against Lancelot's. He's einherjar-fast, but that just results in his body twisting into a weird contortion that tells him his moves were definitely too wide and obvious and absolutely not economical enough.

But knowing the error he made is pretty cool, actually.

With a grin, he drops to the ground, confident that his athleticism and reflexes will serve him better by disengaging and then rising again than by trying to recalibrate and block.