Heart of the Swarm- Evolution Guide: Ruuuuuuush!

The zergling evolution mission opens on a planet where a Dominion base rests atop a plateau, rendering zerglings incapable of reaching it.  Abathur immediately presents you with your solution- a local race of semi-avian beings possess the capability to leap up and down cliffs, and use this ability additionally to pounce on their targets from a distance, striking immediately.  You are directed to send a small force of zerglings after these ‘karak’, and kill them to obtain their genetic data.

Once you have done so, Abathur weaves this into the zerglings’ DNA, and then delivers you an additional, larger batch of raptors.  You will need to take all of your raptors and charge to the top-right area of the map with an attack-move command.  The ability to leap cliffs and pounce from a distance will make short work of the terran outpost, demonstrating the ability of raptors to more easily handle not only cliff fortifications, but also enemies with minimum ranges and/or slow firing rates, such as the siege tank camped in the midst of the terran main base.

You are then moved to a different location and given command of a ‘rogue brood’, which includes a zergling variety dubbed ‘swarmlings’.  These zerg come in groups of three from each egg, thus allowing you to quickly amass a much larger number of them than you would regular zerglings.  You can then charge up to the top-right again, and watch them puddle around the feet of the enemy thor and erode it to nothingness.

This basically demonstrates the point of the two evolutionary strains- Raptors are more efficent zerglings, and swarmlings are less expensive zerglings.

Raptors tend to be extremely effective in situations where they are among other breeds of Zerg that move at roughly the same speed as them- their ability to pounce makes it very easy for them to provide one of the two main functions of zerglings: getting in the way of enemies killing your more valuable units.  This also helps them bypass their own frailty a bit, as enemies with ranged attacks will get fewer chances to shoot them before the airborn raptors land on their faces and start cutting.  The leaping function also makes them incredibly versatile on maps with varied terrain levels, enhancing their early quick-strike capabilities and allowing you to assault from odd angles in much the same fashion as the Terran reapers.

Swarmlings are only useful in the same situations normal zerglings are useful in.  However, you essentially get one broodling free for every two you buy- each egg spawns three of them, and each of them only takes a third of a control point.  This results in quickly mounting numbers.  They also spawn in less than a quarter the time it normally takes for a zergling egg to gestate, meaning they make excellent defenders for surprise attacks, provided you have the minerals to afford a worthwhile number of them.  Being the most ‘disposable’ form of zergling, broodlings are also useful when you want a defense or offense force that will both be inexpensive and die off as you move on to more advanced units to replace them.