The Devourer is a rarely used Hive-tech exclusively air-to-air unit that requires a Greater Spire to morph from a Mutalisk, through a Cocoon. While technically effective in its role as an expensive, powerful anti-air unit it rarely fits the meta as Zerg rarely requires having to tech-up and pursue air superiority. It deals decent but slow single-target damage, somewhat outweighed by its cost, but its main trick is applying a unique, stackable debuff called Acid Spores in a splash. Spores add a point of damage to every attack and slows attacks its target makes, making them extremely powerful with Zerg Mutalisks which bounce attacks thrice. The fact that this splashes makes Devourers powerful in large-scale air battles. It is somewhat hampered in this by the fact that the Devourer is slow-moving, if faster than the Guardian, meaning it can be outmanuevered and largely is used as a defensive unit or in a final-battle scenario. They are abetted however, by their large healthpool and high armor, which makes it largely impractical to focus them down and their range is above that of most air-attacking air units. They also have a cost more leaning toward minerals which can be just the thing from a gas-exhausted late game Mutalisk army.
The Acid Spores are a unique debuff caused only by the Devourer. Each unit hit by a Devourer's attack -including the ones within one matrix of the target that are affected by splash- receive one Acid Spore per hit to a maximum of nine. Note Devourers technically are not useful past the point where their debuff is applied.
The primary effect Spores have is that for each Spore a unit has stacked on it, it takes one extra damage per attack. For example, one Mutalisk would deal 9 points of damage to the first unit its Glave Wurm would hit, 3 points to the second and one point to the third. If however it attacks a group of units affected by nine Spores each, the Mutalisk would deal 18, 12 and 10 points of damage respectively. This is why Devourer-Mutalisk is such a powerful combination. Devourer + Corsair or Valkyrie are much more powerful combinations and can wipe out all air with comparable cost. Additionally, for each Acid Spore attached to a unit, that unit's cooldown is increased by approximately 12.5% unless offset by the hard floor of 3 ticks. Note that the Protoss Carrier is not affected by Acid Spores in this regard since it doesn't attack directly.
The Acid Spores will also reveal any units that attempt to cloak; however, this effect must be present on the target prior to its cloaking. Cloaked units that are not detected and not already affected by Spores will not have Acid Spores placed on them.
Devourers can be a critical unit in maintaining air control in Mutalisk vs. Mutalisk battles. The bouncing attacks of Mutalisks (and to a lesser extent, Hydralisks) benefit greatly from the splash effect of the Devourer's acid spores, which will likely affect multiple units due to the Mutalisk's tendency to stack together. In addition, the Devourer's 2 base armor helps mitigate damage taken from other Mutalisks. The fact that Devourers come with Guardians means that Spore Colonies can be made less of a threat.
In a Mutalisk/Devourer mirror match-up, it would be better to target the enemy's Mutalisks first. Since the Acid Spores will likely be in full effect moments after the engagement, the relatively low hit points and high damage output of Mutalisks make them better targets. The proper way to spread out shots from Devourers against Mutalisks is to attack move at a spot in between your units and his.
High level Zerg vs Zerg games however very rarely reach the Hive tech stage (the only case — indecisive midgame from both sides) and therefore Devourers are not often seen in this match-up.
Although the Zerg vs. Terran match-up occasionally sees aerial combat between Mutalisks and Wraiths/Valkyries, it rarely persists into the late-game when Devourers are finally available. Nonetheless, the Devourer's Acid Spores are very effective against Battlecruisers and Valkyries (which already have high attack cooldowns) and Wraiths (since acid spores reveal cloaked units.)
Devourers are used to counter massed Carriers, usually used in conjunction with the Defiler's Plague, Mutalisks, Scourges, and Hydralisks. They are also a good counter to mass Corsairs due to their high defense. However, like other air units, they are very vulnerable to Maelstorm, Psionic Storm, and Archons.
- The mineral, gas, supply, and time cost are all taking into consideration the cost of the Mutalisk.
- type-b vs. ZerO on Match Point, NATE MSL, Ro32 Group G Losers — example of a late-game Zerg vs. Zerg with sloppy midgame.
- RorO vs. ZerO on Polaris Rhapsody, Shinhan Bank Proleague 09–10, Ro5 Week 6 Day 2 1st set — another one.