There were a few things about the way his kick landed that felt wrong, incredibly wrong.

Just before it would connect, Alexis went in for a grab - which, frankly, wouldn't help at all had she been an ordinary human. It could prevent damage to her vitals, but ultimately, she would still end up on the ground without even the chance to gain an advantage from controlling her opponent's leg. A single strike from Vos'stoorge's sword would put her to rest in the first few seconds of the fight, granting him a flawless victory along with entry to the next round.

However, it seemed that fate had something different in mind for him. Alexis didn't even budge one bit, holding still in mid-air same as a brick wall holds on ground. By the virtue of some incredibly powerful force, the girl both defied gravity and staved off a mighty kick with nonchalant ease. Perhaps, she was using some sort of levitation magic; for Vos, knowing exactly what it was happened to be the least of his concerns, him being unprepared for this kind of situation. Taken by surprise, only a mix of pure instinct and combat acumen guided him, years of training surfacing that very moment. The decision came to him fairly quick: without any footing and nothing to grab onto, chances were he wouldn't be able to yank his leg out of her grasp, so there was only one course of action left to take: offense. He had to either pressure Alexis into releasing him, or end her here and now.

While the momentum of his kick would still be surging through her arms, straining the muscle, Vos would bend his leg, bringing himself closer to Alexis, and then hook his left shin around her thigh. While this would put him into a strange position, the right shin till perpendicular to her body, this also provided more muscle power for him to use, allowing Vos to pull himself upright, bringing his knee towards his opponent's chest with the strength of both of his legs and his hips. Only having to overpower her triceps and forearms to do so, the mageblade would manage to cover their gap in physical ability this way.

Thanks to doing so, he would be right up in her face, while Alexis would still have one hand wrapped around his ankle and the other trapped in the crook of his knee, the unnatural hardness of Vos'stoorge's muscle making it harder to escape than one would expect. He would lose no time - launching his kick, he brought the dagger arm back to his chest instead of keeping it overhead, and now it would be primed to strike. A quick jab towards her face - and even if she leaned out of the way, avoiding imminent death, he could still hook the dagger around her neck on its way backwards and simply activate the Pulse spell, sending the shockwave right into the base of her skull; an attack that could either knock her out cold or rip apart the spinal cord.

All of this, from the moment Vos would realize he was trapped, and up until he would thrust his dagger into his adversary's face, would take less than a single second, fused into a single, fluid and captivatingly deadly motion of the body.