When the Ultralisk and Roaches come, you can retreat across the chasm with your Stalkers. There is an Overseer flying about - try to take it down as well. The Mutalisks will hit you first, so take those down. At this point, be careful because a Zerg attack is coming consisting of a few Mutalisks, 4 Roaches, and an Ultralisk. You'll soon come across a location where there are tons of Scourge flying chaotically. Just slowly advance through the mission, and don't rush things. This is perfect for taking down units without getting overwhelmed. When you reach the Stalkers, you can start luring enemy units away to attack them one at a time. Use Zeratul's ability to freeze all detector units you see, and destroy any attacking units you see. The beginning parts of this mission aren't too difficult. You start out with only Zeratul, but you'll eventually get 4 Stalkers, and there's another checkpoint where your Stalker count will be replenished to 5. This mission is a simple dungeon crawler type mission.
