'Three seconds…' Xavier thought after delivering the kick to the chest of the Lord, sending him tumbling back.
Three seconds…
That was how long he could safely change his density for. He had increased the density of his leg for just a moment to deliver that heavy blow, but because the air around the Lord was still burning hot — despite the blizzard from Glazier — he noticed that the longer he held the form, the more his leg absorbed the heat. Three seconds seemed to be the only safe window he had before the heat soaked too deep, leaving him with internal burns and injuries that he couldn't afford to deal with right now.
Xavier adjusted his grip on his sword, but he didn't immediately lunge after the Lord because he had already used his moment of surprise.
And lunging in blindly to follow up would be like trying to hug a cactus while covered in honey.
Instead, he waited because he trusted that Alicia would find her own opening to aid him, and of course, she did.
