Worlds of Magic: Planar Conquest (JP)

This is the best strategy that I found for this trophy:

1. Start Single Player Game.
2. Select any plane with Terrain set to Pangea and Landmass set to 30%.
3. Opponents: 1.
   World Size: Normal
   Difficulty: Adept
   Resources/Neutrals/Features: Scarce
4. Faction: Orcs.
5. Use any Sorcerer Lord.
6. Save at turn 1.
7. Cast Magic Spirit (everyone gets it) and use it for multiple turns to find the opponent's starting city in the cloud of war. Summon as many as you want.
8. Once you find it, remember exactly where it is and reload your save at turn 1.
9. Train as many units as you can to completely fill your starting food limit. Make sure they only take 1 turn to complete per unit.
10. Once you hit that limit, sprint to the enemy city. The opponent should be exploring and their capital city should be a very easy target. Doing this I was able to complete games in 20 turns or less with ease.
11. If the game does not end then the opponent was able to get a second city in time so take it out too to end the game.

The trophy unlocks during the Result screen at the end of the game.