The battle that followed left Lex unusually flustered. Their camp's defenses, despite only having just been built, seemed impenetrable, which meant there was no actual threat to Lex. But at the same time, he couldn't just relax or focus on something else, because if the defenses fell short, he would need to protect himself.
He couldn't participate in repelling the attack because, frankly, he was too weak to make a meaningful contribution. He couldn't even watch the fight because if he came too close, he would make himself vulnerable to shockwaves from the battle, and might even get in the way of his allies.
In the end, he spent multiple hours just… waiting for something to happen. In the end, the battle ended with their camp managing to defend successfully. Ptolemy, afterwards, went into the forest with a few guards, and though he did not say what he did, assured the camp there would be no of such more attacks once he returned.