Plague is an offensive spell cast by the Zerg Defiler that infects any unit or building with a 4x4 matrix of the target with a splash of red goo. Plague deals four damage per tick over 600 frames, at a rate of one tick every eight frames. This equals around 11.8 health points per second over 25 seconds at Fastest game speed. Each tick deals four damage unless the unit has four or less health, in which case it does nothing. This does not end Plague; it continues to check if the unit has five or more health for the duration, and deals four damage when it does.
Thus, Plague alone can never kill. Still, the effects cripple units struck. Even a powerful unit can be killed in one hit after enduring Plague; for instance, a single Mutalisk could kill three Science Vessels with a single attack.
Protoss endure Plague well; Plague ignores and has no effect upon Plasma Shields, instead damaging the core hit points beneath. As with other goopy spells like Ensnare and Acid Spores, Plague reveals cloaked units for the duration. Plague does not infect Burrowed units, but a unit with Plague that Burrows continues to take damage. Similarly, Plague does not infect units inside transports or bunkers, but Plagued units continue to take damage if they enter.
In competitive play Plague is a costly but devastating spell. Its requirements leave it unavailable until late game, when it plays a great role if gas costs allow it. Because of the cost and tech it generally isn't found in ZvZ.
Players often use Plague against MnM squads, which tend to clump in great numbers. A well-placed Plague sends them scampering in retreat as they stand no chance against the Zerg onslaught. Additionally, Medics try to heal the afflicted units and deplete their energy in vain, crippling them for some time even after the Plague expires. If Vessels appear, they become the target of plagues, then to be sniped by a single Mutalisk.
Plague goes unused versus Terran mech builds; the game tends to remain at Lair tech, the larger mech units are harder to afflict en masse, and Defilers tend to get sniped.
Though not as effective against Protoss (who retain their shields), Plague still finds some use in this matchup. It tends to play backseat to Dark Swarm if the enemy uses many Dragoons, but in the late game, it can deplete the vitality and staying power of Protoss armies, leaving them vulnerable but preserving their full Psi cost. This weakens the Protoss army but prevents the units' being replaced once near the 200-point supply cap.
Despite the high cost and uncommon tech branch, Plague can find use in late ZvZ. Adrenal Gland-upgraded Zerglings under Dark Swarm shred Plagued enemies. Consume boosts the Defiler's energy by 50 per snack; thus, three Zerglings (75 minerals) fuel a Plague, which will result in the deaths of many more enemy units. Because they tend to stack, air units are particularly vulnerable to Plague; it devastates Mutalisks, Guardians, Devourers, Queens, and even Overlords. Even Scourge are less likely to reach their targets. If you opt for Plague tech, the enemy air force will be larger and stronger than yours, but a single savvy use of Plague more than offsets this disadvantage.
In Combination with Other Spells
- Units in Stasis cannot be infected with Plague and cannot take damage. Since Stasis lasts longer, Plague will do no further damage.
- Plague can be "recalled" by enemy Arbiters. This Plague + Recall replay is an example of Plague + Recall effect that was caused at about 39:10 when Recall from center to 3 o'clock natural was done and Plague was casted to center. The animation of Plague was shown at center but effect (units and building affected) was applied at 3 o'clock natural, infecting the recalling Arbiter, as well.
- Plague dispels Hallucinations.
- Plague damage stacks with damage from Psionic Storm and Irradiate, but not from another Plague.
- Plague infects and damages units in Maelstrom and Lockdown.
- Restoration cures Plague.
- Defensive Matrix and Plague do not interact with each other in any way. However, if a unit's health drops to one, it may be possible for damage "leaking" through the Defensive Matrix to kill.
- Defilers cannot self-target with Plague and are immune to their own Plague, but will be infected by another Defiler's Plague, even if it belongs to the same player.
- Plague carries over to both types of Archon if either Templar was infected.
- Plague carries over to Zerg buildings and morphing units. Note that units emerge from eggs and cocoons with full health, even if they remain infected.
- Plague will damage units in a gas station or a transporter.
- Plague never affects Protoss shields.
- Interceptors flying back to a Carrier will heal up and be sent out when they are back at full health. Casting Plague on the Interceptors will cause them to remain in the Carrier until the spell wears off, consequently disabling the Carriers from attacking. Though players still contest its fairness (and its status as a "bug" at all), it remains legal in Professional StarCraft as well as on ICCup.
- https://www.youtube.com/watch?v=Vpuv7VPb2rA - PLAAAGUUUUUUUEEEEE
- adapted from: Zerg Strategy Guide <http://classic.battle.net/scc/zerg/special.shtml>