Parasites aren’t actually parasitic at all, but are large monsters generated from Wormwood. In ancient times before the Unholy Host, Wormwood sometimes created the creatures as ‘antibodies’ against the odd invader, and carrion eaters to keep the environment neat. These days, while parasites are occasionally summoned and controlled by the forces of Light, they’ve become a trademark of the armies of Darkness, especially of Lord Krikton, who has created many varieties of parasite.
Parasites all take the form of arthropods or giant worms. A very few, like the Battler, are hundreds of feet long or tall and serve the Host as vehicles or giant monsters to rampage and destroy the cities of Light.
Battlers are huge spiny things with rending claws and a spiked mace tail. Time to break out the Battle Saint when you see one. Ticks and Beetles are small enough to serve as mounts, and can fight on their own with great fanged maws and mandibles that can snap a man in two. Monster Worms grow to be 4 feet wide and 30 feet long, Tangleworms have similar size and grow tentacles.
Krikton Flailers are man-sized insects with long worm-like tails, they are his ideal minions. Krikton Leapers are Tyranid-looking 12 foot tall mounts that can jump 100 feet long/high, and reach a speed of around 100 mph (160 k) by leaping. Krikton Battlewagons are like larger, far more armored versions of the Leaper that skate around on wheeled feet and have 4 “guns” that shoot sharp spines. All are named in honor of their creator Lord Krikton, who made them from whole cloth instead of corrupting and enhancing existing parasites like those above.