The guardian is virtually identical to its StarCraft counterpart, a slow-moving but long range aerial siege flyer. It appears as one of the zerg breeds in the Amon Brood in the Legacy of the Void campaign and as a feral zerg breed in Nova Covert Ops.
Guardians gain +3% hit points, +1% attack speed and +1% Biotic Leech per stack of Biomass. Can stack up to 100 Biomass. Passive: Heal 1% hit points per Biomass.
Essence Hoarder: Guardians can collect an additional 25 Biomass (summary 125).
The Limitless: Guardians can collect an additional 100 Biomass (summary 200), but gain +1.5% hit points, +0.5% attack speed and +0.5% Biotic Leech per stack.
The amount of collected biomass vary, based on difficulty and the amount of supply consumed by the killed enemy unit:
Collect 5 biomass per supply (Casual and Normal)
Collect 4 biomass per supply (Hard)
Collect 2.5 biomass per supply (Brutal)