I have been thinking about a hermetic waterwheel. The reason I have been thinking about this is because the waterwheel is the dominant form of power that is not muscle based in medieval Europe and by the 13th century was becoming widespread.
So I started to think about how to make one for a covenant, and came up with this:
Make a 5m diameter waterwheel, which is large but not unimaginable large in the period. At the top of it, put an approximately 4 meters in a side cube, made of some waterproof material. This is again very large, but not unusual at all. Dig a lake under it.
The enchant an item that produces water using craq guideline of 2, touch range, diameter duration, unlimited uses. Level 14, you could power up by a factor of 10 for only one more level.
The individual for aquam is a body of water of about that volume. If you want to go level 15, you can make it 10 times bigger.
Power works out at about 100kw (roughly 135hp) That is a lot, but again it is an amount that is only double what the forge mills in France and England were using at the time.
This would be incredible for mining on covenant ground as it could haul all the rock and the water would not flood the mine as it disappears.
You could use it for drop forged as the French and English are doing at the time, for massively helping iron production.
1203 has a tool sharpening mill in France, and tanning and fulling mills are fully a hundred years old.
The key thing here is how simple the enchantment is. What other enchantments are also
a) in period (industries were massively improving water power use in 1220)
B) cheap and efficient