The basic ability of Defilers does no damage, but it penetrates any shield and weakens enemy armour, allowing the spikes, claws and acid jets of other Xerj to do more damage in future attacks. Plague-affected armour takes triple damage from direct attacks, with weakened areas being attacked first. A target can accumulate a maximum of one-third of its armour (in which case all of its armour will take triple damage).
For example, a defiler with the plague shot 250 hits a cruiser with 2500 armor. The cruiser has 2500 armor 250 of which are plagued. The next shot made by mudkip has the attack power 10. Mudkip hits the plagued armor and the force of the shot triples. The cruiser now has 2470 armor, and 240 armor remains infected with plague.