Out Of The Abyss
Sarith is a male drow, which surprised you considering he was in prison with you. He was largely unapproachable (that much didn’t surprise you), and he tends to rebuff attempts to speak to him.
You have found out that he was sentenced to die for the crime of murdering another drow in a fit of madness. Sarith has no memory of this, and suggests that it is a plot by the other drow to discredit and destroy him.
Oddly, Sarith did mention that a supply patrol from Menzoberranzan (The Drow City Of Spiders) is overdue, which is unusual, and that there is a gray ooze in the pool that feeds on the waste from Velkynvelve. He assured you it is harmless so long as it is undisturbed.
When an elite drow warrior your party had taken prisoner in the Velkynvelve questioned Sarith about him allying with “surface dwellers”, Sarith calmly walked up to the man, stabbed him in the throat, bled him out over a cliff, then tossed his body down to the spiders below. Sarith said that this would distract the spiders, but it was said in such an off-hand manner you’re not sure you believe him.