Dr. Jekyll is a random event in which a man appears and urgently asks the player for help. If talked to, he requests an identified herb of the player; If the player has an herb in their inventory, he will take it and give them a potion, if the player has no herbs he will give the player a strength potion(2) before disappearing, saying he isn't safe with it.
If ignored, Dr. Jekyll will turn into Mr. Hyde (level 14-159, depending on the player's combat level) and attack the player. If killed, he would drop a potion, similar to if he was given a herb. However, sometimes he drops an empty vial. Killing him can sometimes be more profitable than giving him a herb, as he could possibly drop a Super restore potion(4).