New units
Lurker
Same as the lurker in Brood war and Heart of the swarm only this time have long range. Effective against large numbers of ground enemies but keep them away from any detectors and enemy air power like banshees, mutalisks and void rays.
Ravager
Evolved form of the Roach. This unit is a siege unit that makes death upon immobile targets like siege tanks, lurkers, photon cannons etc. but still weak to marauders and banshees.
Infested Banshee
Same as the Terran banshee except it can burrow.
Infested Siege tank
Same as the Terran siege tank except this one is infested and can only attack while rooted to the ground.
Volatile infested terran
Same as the infested Terran fron the original starcraft only this one does bonus damage to the buildings only.
Infested Liberator
Same as liberator only it cannot attack ground units ever.
Infested Diamondback
Same as a the regular Diamondback but it can bring air units to the ground so it can be attack by ground attackers.
Modified units
Baneling
Health increased from 30 to 40.
Infestor
Can use all abilities while burrowed.
Brood lord
Range decreased from 11 to 10.
Swarm host
Swarm Host cost reduced from 150/100 to 100/75 and increased Locust Swoop range from 4 to 6.
Ultralisk
Their armor upgrades can go all the way to 7 which is more armor than even a fully upgraded battlecruiser.
Corruptor
It has the new Caustic Spray ability which replaces corruption. Caustic Spray is a damaging ability.
Returning units
Devourer
This brood was unit is massive, exclusive to Abathur and it does bonus damage and splash damage to armored targets. Its acid can stack up to 3 times unlike in Brood War.
Guardian
Same as the one in the original starcraft.
Queen
The Queen from Starcraft 1 has returned only it cannot infest command centers.