Ive had some experience with Machaka in PBeM, though as it was my first, and after only a couple days of owning the game, probably my least successful
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Ulm is pretty weak to magic. Some ideas:
-Swarm. Cheap, Lasts 2-3 rounds, a good way to soak up enemy fire/lances. Little bugs tend to kill themselves when they get repelled, so it wears itself out quickly.
-Blindness. Not a bad choice against Ulmish Cavalry. Also cheap, easy to research, works well with 80 gold Doctors.
-Fire Archers. For some reason ive never tested fire arrows, even in single player. My comments here would be that Archers are extremely vulnerable to Blade Winds, which Ulm has no trouble casting in large amounts. Even Machakan Hoplites get smacked down hard by Blade Winds.
-Destruction. Earth 3 armor defeating spell. Hard to get unless you have Ainra or a Earth Pretender, and somewhat random in its targeting, esp., if the enemy has spread his formations out.
-Seven Year fever can disease his army if you dispair of killing it outright.