While your army is besieging, you can exchange the accumulated robbery tokens for the resources in Treasury of the besieged settlement
Each raider unit generates 5 Robbery tokens per day
1 robbery token can be exchanged for 1 unit of one of the four resources
When exchanging a token robbery, there will be a permanent penalty of 30%, as a result of which the treasury of the besieged player will lose 1 unit of the resource, and you will receive only 0.7