Poison Damage is a type of damage in Titan Quest. It is reduced by Poison Resistance.
Poison Damage is almost exclusively dealt as damage over time (DoT). Its default base duration is 6.0 seconds, making poison the 'slowest' killer of all damage over time types. Poison is not considered an Elemental Damage. Poison damages increase by 10% per 50 Dexterity ( in Titan Quest: Anniversary Edition ). Also its effectiveness can be increased via skills and items.
The Rogue Mastery has various skills dedicated to this type of damage.