Projectile modifier spells that add an arc of material between multiple projectiles. Arc spells require a minimum of two projectiles in order to function
This modifier creates poisonous particles to flow between fired projectiles, inflicting that status on any creature caught in the streams. Unless the spell naturally produces more than one projectile per cast, like Triplicate Bolt, it must be used with a multicast modifer to work.
As poison is more dangerous to the player than the enemies, and no perk existing to block the effects, it is questionable whether there is an effective way to use this modifer.