After eating, the two once again found somewhere to hide and wait out the time, having no real goals to move towards. At one point Ron stepped on a snake that Thirteen had been too tired to warn him of, but managed to avoid its strike through purely panicked reactions, following which Thirteen skewered it.
When the heavy blade made contact with the serpents dead, bark-like exterior, it splintered and crushed the shell, but was unable to sink into the flesh beneath. That bark-like exterior was in fact an incredibly tough natural armor.