Apply Poison IV is a toggle skill in AION Classic 5.0. The Assassin learns it from level 51.

Learned by

Class	Faction	Character level	Skill level
AssassinLearned automatically	Both factions	51–59	1–9
AssassinLearned automatically	Both factions	71–75	10–14

Taught by

Item	Skill level
Apply Poison IVAssassin (Skill Book)
[Event] Apply Poison IVAssassin (Skill Book)