Please edit if you feel that this information is outdated, insufficient, or wrong. Feel free to create a section for the other variants if you have more information.
For all maps, I recommend launching it and activating it as a skirmish map draft (long click on incomplete map) to get information concerning the units and triggers. Unfortunately, some maps are of the old kind (TMX) and only show grassland in the draft.
Age of Strategy
Easy
Beginner's Manual
This campaign is quite easy. Just attack the enemy and you will win. However, it is harder to complete the 2nd and 4th maps within the turn limit.
Newbie Challenges
This campaign is easy. I like using units with power range and bonuses towards buildings (Zweihander Wielders, Gallowglass).
Snowy Campaign
This campaign is quite easy. However, to get three stars in the first map, you need to block the bear, which will spawn on the left at turn 3.
Revolution
This campaign is easy despite the size of some of its maps, so if you want to, you can unlock the next map with the unlock map spell without finishing the previous map.
Grim Company
This campaign is also easy. Remember not to kill the neutral saracen rider and champion, and send the hero knight to meet the saracen rider and the templar with a name to the champion.
Gorgon Delight
This campaign is also easy. Frisian Horses are very useful on the second map. Map 4 is slightly harder, and remember to attack the enemy spearmen with your hero knight to avoid counters.
Carnage
This campaign is easy to complete, however it is recommended to unlock some upgrades before starting some of the maps. The map sizes are also very large.
Challenge
These maps are somewhat harder than the previous ones, but the turn count is very loose.
Almost Got It
These maps are somewhat easy. It is harder to complete some maps within the turn limit.
War of Factions
Please give more information if you can.
Medium
Heir to the Throne
Try to kill the critical units before other triggers activate.
Viking Age
Attack, don't defend.
Two Kingdoms
Please give more information if you can.
Paths of Rome
Medium difficulty. It is recommended to take a look at the map draft.
Aquarias
Interesting maps, check spies in map editor.
Brothers War
Please give more information if you can.
Fire War
Please give more information if you can.
Rise of Namu
Build objects, especially Frisian Horses.
Asgeir
Some maps are somewhat harder.
Hard
Power Creep
Maps are relatively easy, although it is harder to get 3 stars on some of the maps.
Kingdom Come
Intricately triggered. To find coolguy, take a look at the triggers.
Puzzles
Not especiallly hard until map 6.
Maximus
Please give more information if you can.
The Rebel King
Not very hard. It is better to delete the gates (in map 1) first.
Suhari Kingdom
Difficulty ascends as campaign progresses.
Owaguchuk
Please give more information if you can.
Mercenaries
Please give more information if you can.
Ambition
Longest campaign, tied with Asgeir. Increasing difficulty.
Nyadhos Strategy
Please give more information if you can.
Age of Nyadhos
Please give more information if you can.
Hornburghs Dominion
Please give more information if you can.
Prison Planet
Remember that you can change the colour.
Savage Story
Pay attention. Also take a look at the triggers.