[ The aura coming off of the other Servant is twice as powerfully dark to Saber, and he's already woven his armor around him because of it, Excalibur with Invisible Air bound to it in hand. He cautiously approaches the man while he watches him succumb to his affliction and the only reason Saber thinks he knows what it is that ails him is because he's seen symptoms like his before. ]
I can't imagine you're particularly friendly to the others, so that would explain what the problem is.
Option 4
I can't imagine you're particularly friendly to the others, so that would explain what the problem is.