This category pertains to the "Monsters" launched by certain mobs (usually Mages) at the player.
“Spores are hostile projectiles spawned by Plantera. They can be avoided by being hit, or shot...Spore
“Burning Spheres are magical projectiles launched at the player by Fire Imps. They have 1 HP and...Burning Sphere
“Water Spheres are projectiles launched by Dark Casters. They have 1 HP and can be destroyed with...Water Sphere