Aboleth oil is impossibly rare, and incredibly dangerous. Coming into contact with it accidentally can quickly spell death for most creatures.

• Acquisition: This poison must be harvested from a recently dead or incapacitated aboleth. It requires no further preparation.
• Market Value: 2,500gp
• Legality: Illegal
• Modification DC: 25
• Medicine DC: 27
• Saving Throw DC: 14
• Effect: A creature subjected to this oil must make a Constitution saving throw or become diseased. The disease has no effect for 1 minute and can be removed by any magic that cures disease, but the creature is unaware that they have been affected. After 1 minute, the diseased creature's skin becomes translucent and slimy, the creature can't regain hit points unless it is underwater, and the disease can be removed only by heal or another disease-curing spell of 6th level or higher. When the creature is outside a body of water, it takes 6 (1d12) acid damage every 10 minutes unless moisture is applied to the skin before 10 minutes have passed.