"Mercenaries and Artificers govern the Factories, wherein tamed, exotic monsters fight side by side with products of advanced technology, such as mechanical constructs and humans equipped with guns or flamethrowers."
Grail Structure. +5000 /day, +50% creature growth Strikes all enemy stacks with lightning first round of the controller's turn. Occurs in every battle the player participates in, anywhere on the map. Damage is based on the number of buildings in the grail town.
Despite its expensiveness Factory can choose one unit line-up and develop it quite quickly.
Factory has 2 mechanical creatures which can be repaired (i.e. "resurrected") if damaged.
Factory towns can "earn" 5-day income (2500 gold) in advance using Banks every 5 days. Banks are strategically useful at early game, so could be used to faster max upgrade halls and other income-based buildings in order to have great economical advantage at early game and further.
Halflings are possibly the best level 1 unit. They shoot, like Master Gremlins, but have higher stats and an extra ability (ignoring enemy defence).
Automatons are among the best level 4 units, with no enemy retaliation ability. They can be used as tanks early on and repaired with Mechanics or used as suicide-bombers with their Detonation at death ability, which allows them to explode and deal significant damage to all creatures surrounding them. This can be used early in the game to defeat much stronger enemies.
Native terrain is wasteland, which makes it harder for other units to traverse (however, movement penalty is lower than for snow or swamp, which are native terrains of Tower, Cove and Fortress, respectively).
Excellent Grail building; Lightning Rod can wipe out the entire army of wandering creatures, or deal significant damage against enemy hero's army. Sending multiple heroes a turn with no army when one of the allied Factory towns has the Lightning Rod can clear almost all enemies, except for units that have Spell immunity or a Spell Damage Reduction. This is the only type of Hit-and-run allowed since patch 1.7.
Cons:
Factory is an expensive town. To have both unit line-ups a lot of resources is needed (70 Crystals just for the lvl 7 creature dwellings and their upgrades). On top of that, it has among the highest ore spending on all buildings, and the highest army cost (even when comparing 7 vs 7 units, and not including the level 3 Bellwether Armadillos).
A lot of the Factory units are quite weak in comparison to other creatures of the same level, especially when unupgraded (especially Armadillos and Couatls).
Most Factory units are quite slow (only Automatons, Sandworms and Couatls have at least 8 Speed), and a lot of the units have very low HP (Halflings, Bounty Hunters, Couatls are among the most fragile units for their respective tiers).
Factory doesn't have 1-4 level flying units. All other towns besides Inferno and Stronghold have at least one. Their only flying units are Sandworms (level 5) and Couatls (level 7).