Heart of the Swarm Campaign- Zeras: Waking the Ancient (Part 3)

Make sure you keep your attack force on hand when you have a drone collecting meat- while the primal Zerg aren't fast enough to catch up once the drone is on its way back to the ancient, they will attack while it's gathering the meat.  The majority of the attack forces will consist of roaches and hydralisks backed up by two to three guardians, so ranged attackers are a must, particularly the hydralisks and queens that you need to kill the airborne units.  If you keep your eye on the direction they’re coming from, you can usually strategically place your attack force to protect multiple sources of biomatter at once, thus easing the load on your unit management and resources.  Keep in mind that the viable paths throughout the map aren’t always obvious- there are a number of places where the continued presence of the fog of war masks an actual obstacle such as a cliff that means using a round-about method to get from one place to another (and often passing through one or two clusters of enemy units in the process).  It’s up to you to decide if this makes mutalisks more valuable (they go directly and don’t worry about terrain so they can arrive faster) or a liability (they arrive before anything else and are frail, so they get killed by enemy units before the rest of your force arrives).

Once you've collected enough meat, Brakk himself will show up, accompanied by a small assault force, and move to attack your base.  He will appear in his own camp in the Southeast corner (even if the camp itself has been killed off), and make his way first to any outposts you've established and then, once those are destroyed, to your main base.  While the primal guardians that accompany him aren't anything special, Brakk has massive health and a powerful area attack, so zerglings are of very little use here, and you need a full-on assault force to really take him out- or mostly just Kerrigan to disable him while he's under attack.

Once Brakk is finally slain, the ancient will awaken at last and pull himself partway from the ground.  A brief discussion with Kerrigan ensues, leading to your next mission...