Heart of the Swarm Campaign- Zeras: Supreme (Part 2)

This leaves you on the South end of a rather large island.  On your way to the bulk of it, you will have to face down a primal ultralisk, and within the center, another ultralisks accompanied by a pair of hydralisks.  Before moving to the East, you will want to send Kerrigan North off the edge of the landmass- there is a small crevasse full of primal zerglings that also contains a Xel'naga relic.  A quick leap-and-dash should clear the enemy units out and land Sarah on the needed artifact.

Another cluster of ultralisk and hydralisks waits to the Southeast, and then the path narrows again.  An additional pair of roaches will join you here, only a short distance before the lair of the first primal pack leader, Yagdra the flaming worm.  Your best bet on the roaches for this fight is to burrow them and leave them burrowed- only one of Yagdra's attacks can actually deal enough damage to kill them while their healing rate is boosted by burrowing.

Yagdra will use three different attacks as you fight it, though one isn't strictly an attack.  First, it will launch fireballs at pre-targeted locations- keep Kerrigan out of the red circle and you'll be fine.  Secondly, it will periodically burrow into the ground and relocate, leaving behind a single ultralisk egg or a cluster of smaller eggs- destroy these with Leaping Strike and Psionic Dash to keep them from overwhelming you with numbers.  Finally, near the end of its life, Yagdra will launch a stream of flame.  This deals enough damage that it can kill the six roaches that have joined you- but it will stay aimed at Kerrigan, so just keep her in a different direction than the roaches are and have her Mend herself as needed while killing the thing with her base attack.

Once Yagdra is dead, Sarah will collect its essence and be ready to move on.  Four hydralisks will join up immediately to the South, and beyond that you will find Kraith's eggs, which are preparing to hatch as part of its pack.  Destroy them before they can become a dangerous enemy force, and then move on to the East.  Take a short divergence to the North after two clusters of Kraith's zerglings and hydralisks to take out three ultralisk eggs and gain another artifact, then resume your Eastward travels.  Kraith's troops will try to ambush the Queen of Blades from a set of three caves- destroy both waves of enemies there to keep from being jumped again.  Deal with the two ultralisk ambushes and assorted other troops before turning North into the sandy area.  Any troops you have lost will be replaced on the path to the next area, which is the large sandy arena where Kraith waits.