The behemoth-like beast almost does win free. Though no more time conscious than Vincent, the beast's 'existence' was tied inexorably with the former Turk. There was a war between beast and human mind, but it was for mental dominance rather than instinct. There'd never been a part of him trying to say 'maybe we should find a nest of sun baked rocks to curl into for the night' while the other said 'it's night, time to hunt'. He was what he was. He was smaller, there were horns on that head to jerk and twist and block any biting jaw as they sought the right angle to hold.

What he had, essentially, is experience being a monster. this kind of monster. One that doesn't get bothered by wounds that would never kill him anyway... what are those teeth, tracking deeper as he pulls and twists? Vincent finds himself nearly free and almost there... When one of the short limbs snatches an extended arm, a part of his mane.

Angrily the beast's tail whiplashes up toward the side of Sephiroth's face- once, twice- but it is too far back to do more than stinging, surprise force. All he needs to do is hold on and put more weight in.