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Scourges spawn in pairs. Patrolling scourges may help deter low intensity enemy drops. Without supervision groups of scourges tend to lock onto and attack the first target that comes into range which may be overkill against low-HP targets (causing scourges to sacrifice themselves needlessly). Using other units to draw enemy fire may allow scourge to hit.
If a scourge egg is hatched after the controlling player is eliminated, one will spawn normally but the other will become blue and neutral.