Defilers are one of the most seldom used units in the game, the reason behind this is the lack of knowledge about the capabilities of this mysterious scorpion like zerg strain. Although a little hard to attain because it requires hive, a defiler mound and a couple of upgrades for it to be effective, the defiler most of the time is ignored. Thousands of zerg lives could be saved while thousands of enemy lives could be taken if the defiler is used properly.

• The defiler is a fairly cost effective unit, 50 minerals and 150 vespene gas for a creature that does a hell of a lot damage and can burrow.
• Its consume ability is a necessity for a defiler to cast spells consecutively. Having a pack of zergling accompany a couple of defilers can devastate an enemy base.
• A tight enemy defense or collection of units, unburrow the defiler a cast plague, consume one or two zergling and cast plague again, flee the defiler or burrow. Plague deals 300 damage but does not kill or affect shields. However, since terran buildings burn when highly damaged, bunkers and supply depots can be destroyed with a plague or two.
• Long range units and tight bunker defense can halt your all out attack. Cast dark swarm over them and before them to prevent siege tanks in siege modes from damaging to the fullest. A heavy zergling or ultralisk attack is a very good combination, the dark swarm nullifies all long range attacks while your zerglings and ultras do the killing. Zealots and firebats will be an easy job for them.
• Hide hydras under the dark swarm and let them stand ground. This is effective for dragoon and marine vs. hydra battles or when your hydras battle masses of air units.
• Attack with zerglings to let a defiler sneak in the enemy base. Cast a plague and burrow the defiler immediately. This will weaken his base and waste his time looking for your defiler.