Look at any game and you can see the reason for a mechanic.
But specifically choosing a mechanic for the world is more difficult to find.
I tried to find a modern example of Mechanics as world building but instead I found that Majesty and Dungeon Keeper, two old games were the best examples.
Majesty has three key elements I want to bring up… the mercenary payment system, movement and the map itself. And I want to compare it to the way Dungeon Keeper does it. But in order to do that I must deal with the “minions” of each game (I may get some mechanics wrong but this is what I see from playing both).
The minions in Majesty are either Heroes or Servants. Servants service or protect your buildings while Heroes will do hero stuff in the classic 5th edition style. Dungeon Keeper’s minions are yours, they are your army and they patrol your locations and effectively, this is a job to them.
So let’s talk income and the two games are different. Majesty has two sources of income for two separate groups. As the King you gain taxes from the various buildings and the heroes gain coin from slaying enemies and taking bounties.
In Dungeon Keeper you claim everything you get in the dungeon and the minions get paid with no bonuses.
Movement is also different, in Majesty, you can only influence your heroes by setting bounties.
In Dungeon Keeper you can pick your forces up and drop them anywhere in your dungeon.
Finally, there is the map Majesty is an open map where units can move throughout.
Dungeon Keeper is very claustrophobic, your units can either stay in the dungeon you have opened up or leave the dungeon, simple as.
This is going to be a long one… in order to do this justice it will be at least a 4 part writing.