Heart of the Swarm Campaign- Kerrigan Abilities: Twin Drones (Level 35)

Twin Drones is a massively powerful ability for your development of force in any map of the Heart of the Swarm campaign.  This passive effect gives you a free drone every time you hatch a drone.  The added drone is completely free- it costs no additional time, no resources, and no control- which reduces your drone cost to exactly the same as your cost for zerglings (unless you’ve gone with the swarmling evolution).  Not only does this save you considerable control costs on your crystal and vespene mining efforts, it also ramps up the speed with which you gain resources to an almost ridiculous degree.  The fact that each building costs a drone as well means that Twin Drones puts a notable dent in your construction costs for your entire base as a mere side effect.  Virtually the only thing that Twin Drones doesn’t do to improve your resource efficiency is increase the maximum rate at which you can gather crystals and gas, which is just as well because you reach the peak of gathering speed essentially twice as quickly as you otherwise would.  This can be absolutely vital during the campaign, as enemy bases start the mission complete while you will often have to construct and develop your base in the middle of a steady stream of attacks from your enemies.  Frankly speaking, there is basically nothing that can be balanced against this ability choice for sheer utility, which makes things a bit hard on Kerrigan’s other fifth-tier options.

While this ability does absolutely nothing about your combat strength (unless you primarily rely on moving spore colonies and sunken colonies around constantly, which is a difficult tactic to make effective, nevermind efficient) it hardly has to.  This tier, and this ability in particular, is all about efficiency, much like the prior tier of entirely-passive ability selections.  Malignant Creep, by contrast, improves your base’s defensibility- which may not mean much if you can’t build up enough of a base fast enough for defending it to matter.  Vespene Efficiency is helpful, but simply doesn’t match the degree of improvement Twin Drones can produce.  On the other hand, producing oodles of drones doesn’t in any way improve the rate at which you intake vespene gas, which Zerg need for everything but drones, overlords, and zerglings, so you could actually find Twin Drones less useful in some situations.

Generally speaking, if you want to make sure you can meet the time-limit requirements for the achievements in the campaign, you’re going to want to either keep Twin Drones in effect, or replay each mission once with it active so you can maximize your speed of action.