Step 1: Infernals
Step 2: Favor of Grum Gog
Step 3: Research Summon Strong Rats they have 20hp, 9 melee attack, inflict plague, and forester. They have no upkeep (only food upkeep) and cost like 10 mana or something
Step 4: DROWN THE WORLD IN RODENTS

in all seriousness this has been my recent early game strategy for impossible difficulty. The rats are fairly tanky with pyromancers supporting them by creating hills so the rats can ward off the AI while you get your overpowered lords and elite units out.