The Defiler ability Dark Swarm is very important for a Zerg player especially if he is playing against Terran, at the late stages of a multiplayer game.The Dark Swarm, eliminates some unit’s attack ability so you can eridicate the enemy army with this selective ability.If the enemy army has high amount of marines,vultures,goliaths,or tanks, this ability will eliminate the enemy capability to attack you so you can easily destroy your opponent.But to use this ability on a widely section, you must research Consume ability which allows you to gain extra mana from your own units life , so there will be a mana recycle by just sacrificing your low cost little Zerglings and obtain extra -we can say firepower-(yes it is power if you think about the enemy units can not damage on you!)But this unit has a diffucult technological development which can make you fail while you are trying to develop Defiler abilities, you must be rich to be rich!