Zerg

(input generic race information here - such as second race created by Xel'Naga... evil, evil aliens!

Storyline

(input the storyline from Starcraft 1 > Brood War > Starcraft 2. Perhaps hide it with Spoiler tags (if possible)

Unique aspects of the Zerg units include

Creep (a terrain effect which is required for all Zerg structures to be built upon (with exception of Nydus Worm and Extractor)
Hatchery - Spawn Larvae (a buff which causes the Hatchery to create a larva every 15 seconds with a maximum of 3)
Queen - Spawn Larvae (a targeted ability which causes a Hatchery to spawn 4 extra Larvae in 30 seconds, with a maximum of 19)
Spine Crawler - Root/Unroot (a morph ability which allows the building to move and relocate itself)
All Units - Burrow (a morph ability which transforms units into their respective burrowed counterparts)