The Drow assassin could have killed Lin Yun and the others. The poison on his Bloodlight Dagger was the infamous Drow Poison.
The poison itself didn't do much damage, but the problem was that its effect was paralysis.
Even the slightest scratch was enough for the paralysis to take effect. It could last anywhere from a minute to several hours. It was extremely potent.
The centaur who had recklessly charged inside earlier had been too careless. The Drow assassin, who had been lying in wait nearby, had stabbed him, and he'd fallen.
The centaur hadn't managed to spot the Drow in time. In fact, out of caution, the assassin had immediately hidden in the darkness when he saw the centaur enter. A Drow assassin, naturally skilled in stealth, wasn't someone a centaur could detect.
Unless the centaur had been like Lin Yun, carefully watching his surroundings with every step and actively trying to spot danger. Even then, given the centaur's abilities, he would've needed to roll at least a natural 20 to notice the Drow assassin in stealth.
So the dagger had practically been a Sure Hit. It struck the centaur, who had very little HP to begin with. He didn't even need to make a saving throw against the poison—he simply collapsed and passed out.
This Drow assassin's class was Assassin, a hybrid of Ranger and Thief. He had an ability called Kill Target: by observing a target for several seconds, he could learn about their likely actions and abilities, improving his use of certain skills against them, such as Sense Motive and Bluff.
As long as someone was his Kill Target, he could study their weaknesses to improve his accuracy and damage. This Drow assassin was about as strong as a Sapphire-level adventurer. Of course, that was according