Toxify is a Green Magick spell and is a higher level form of the Green Magick spell Poison that inflicts the Poison status to multiple targets. Toxify is a Green Magick 4 License that costs 40 LP and consumes 26 MP. It can be bought Rabanastre, Nalbina, Eruyt Village, Mt Bur-Omisace for 4100 gil.
In the Zodiac versions, Toxify has been listed as a Black Magick 11 License that costs 100 LP. Its MP and effects are retained, but it cannot be bought; Toxify is found in a a chest in Barheim Passage's East-West Bypass. This magick can only be used by the Black Mage job class.
Toxify has a base chance of 55% to inflict targets with Poison, but the chance is affected by the caster's magick power and the target's vitality.