Archon
ARCHON - cost: 0 Mineral, 1 Gas
Once summoned, the fiery form of an Archon is a frightening foe. Protected by a massive shield, these units can wade through countless ground and flying units, destroying them with powerful bolts of psionic splash damage. Archons require much time, effort and resources to produce, but are well worth it.
Guardian
GUARDIAN - cost: 0 Minerals, 1 Gas
Although Guardians only cost 1 gas, they also require the "Guardian Aspect" technology and the destruction of a Mutalisk. While this sounds like a lot of resources, it is completely worth the effort as Guardians are strong flying units with a devastating ground attack. Once upgraded, Guardians have the highest ground attack of any zerg unit.
Technologies: Improved Flyer Attack