Vitura

Vitura is a drug that makes its users highly susceptible to suggestion.

History
Vitura was used on a man in 2007 by Chien Na Wei in order to get him to steal a vial of the super-virus, Omega.

Before learning that he had traces of mushrooms in him, Sara Lance suggested that an angry Oliver Queen was under the influence of Vitura, causing him to hurt John Diggle unknowingly.

Vitura was used on Thea Queen by Malcolm Merlyn in order to kill Sara, causing Oliver to have to face the League of Assassins on her behalf and, were he to kill Ra's al Ghul, clear Malcolm's blood debt.

Arrow: Season 2.5

 * "Awakenings" (mentioned)