[Baalz]

Shamblers were key in my success in Evermore with Atlantis. Read my guide to MA Atlantis for more details, but short story is I was pressing an economic advantage and flooded R'yleh with shamblers. The hitpoints and claw attack were great against the low defense, low protection troops R'yleh frontlines, the numbers I was able to recruit them in due to their resource cost was great vs the mind blasters, and the fact that I could recruit from 4-5 provinces right on our border allowed me to hit him everywhere at once. Once R'yleh fell I used my swarms of amphibious troops to hit 11 provinces of Caelum in a sneak attack, capturing close to 20 of their provinces by the second turn of the war.

Cost effective is a relative term.