As William saw Alysis charging the lightning in her hands he had not doubt she was about to throw them. He stamped his mechanical leg onto the snow beneath his feet, it slowly hardening becoming ice and then shooting upwards from the ground to make a wall of ice separating himself and Caster from Alysis, although Caster was now on their side of the ice. But the lightning still blasted through the ice wall due to it being a double cast, although some of its force had been dispelled, causing shards of ice to go flying around.
In that moment though, the small time it took for the ice to break. William had already turned to face the back of Saber, who was moving towards Caster, while Caster was facing saber from the front and was able to keep her eye on Alysis. Caster tried to weave to the left of Saber, meaning if he also turned to meet her, he would be directly in the path of Williams blade. And as she aimed to side step Saber, she thrust her hand out and summoned vines to from the ice ground to try and entangle Alysis.
William and Casters relationship was an odd one but it is what helped them win last years tournament, their roles were reversed yet the could both hold their own in what ever position they were needed to be in. And they fought together, always and forever.