You can kill stuff. You can injure stuff. Just not a night dragon. At least not now, anyways. Aside from it being nearly invisible in the dark, it would freaking fry you. That's non-negotiable.
Just run for now. Maybe toss something at it, but we're trying to get you out into the rest of the Prison Realm for now. Do not waste time trying to kill it. You go against me and try to attack it anyways, I will make your character die, and boot you from the game.
“…Judge not what a man has done, but judge what he could have done if he was a different bloke altogether. For art thou a leper? And a leper can changeth his spots…” --Rudy Wade, Misfits (Series 4, Episode 8)