Miasmic spells were one of the types of Ancient Magicks combat spells that halved the attack speed of Melee and Ranged for a limited time. Miasmic spells required Zuriel's staff to be cast and the special effect only worked on other players, not NPCs. The Miasmic spells were released years after the other Ancient Magicks combat spells, and the spell icons of Miasmic spells looked different. They were removed from the game when the Evolution of Combat was released, and the other damaging ancient spells (smoke, shadow, blood, ice) were renamed and aligned with the four elemental sub-types of damage (air, earth, fire and water).
The four types of Miasmic spells were: