Starcraft Zerg Hive

(Bold text indicates changes from StarCraft)

Zerg Guardian

HP	150	Armor	2	Size	Large
Attack	20 (+2)	Cooldown	60	Range	8
Cost	100+50m / 100+50g	Build Time	40+40s	Control	2
Sight	11	Speed	2.5	Load	-
Morphed from	Mutalisk (Requires a Greater Spire)

These airborne beasts carry symbiotic organisms within their intestines, and use their eggs as long-range artillery shells. When launched, these eggs immediately hatch into small creatures that immediately lunge at any foes nearby. Because these creatures resemble the Broodlings laid by Zerg Queens, scientists suspect that the Queens have somehow transmitted this ability to the Guardians.
When a Guardian attacks any ground unit or building, one Broodling spawns on the center of the target. Each Broodling has 30 HP, does a melee attack (4 (+1) normal damage, 15 cooldown), and lasts 8 seconds before dying. Broodlings provide additional damage, absorb enemy fire, and confuse the ground units' pathfinding AI. This makes Guardians extremely deadly in large groups. Against Terran mech, the Broodlings also cause friendly fire from Siege Tanks and Spider Mines.
The Guardians in SCT are almost identical to the Brood Lords in SC2 WoL. Use Guardians to break enemy defenses and provide support fire. Notably, while the Guardians' attacks are subject to Dark Swarm's effects, the Broodlings they spawn are still effective, as they themselves are melee units. Because Guardians have an unusually long cooldown (60), they are easily overpowered in small numbers--use them with care.
Note: For balance reasons, Broodlings cannot be consumed by Defilers.

Zerg Devourer

HP	150	Armor	1	Size	Medium
Attack	Air: 12v (+1)	Cooldown	60	Range	6
Cost	100+100m / 100+25g	Build Time	40+40s	Control	2
Sight	10	Speed	5	Load	-
Morphed from	Mutalisk (Requires a Greater Spire)

In terms of natural selection, bigger is not always better: while powerful, the Devourer in Brood War was underutilized due to its high cost and lack of a means of attacking ground targets. It appears that many (under progress)

Other Changes

• Defiler
• Dark Swarm
• Instead of making all ranged attacks miss, Dark Swarm now reduces incoming damage from ranged attacks by 50%.
  
• Plague
• Plague now always reduces the affected units' HP to 1 (instead of having 2-3 HP remaining).
• Maximum damage dealt is exactly 300.
• Consume
• For balance reasons, Broodlings can no longer be Consumed.
• Range increased to 1.
  
• Devourer
• Cost reduced to 100+100m / 100+25g.
• HP reduced to 150.
• Armor reduced to 1.
• Attack changed to 12v (+1) / 60.
• Devourers can now attack both air and ground units. Acid Spores affect both ground and air units as well, but do not splash onto buildings.
• Acid Spores duration reduced to 40 seconds.
• Devourers can now properly use move-shot micro without wasting shots.