Warhammer Quest Kingmakers
Where Kingdom Attributes describe the broad and general capabilities and resources of a kingdom, Assets are characteristics with rather narrow usages. Assets can be buildings, circumstances, people, magic, or pretty much anything – they just represent unique advantages available to the kingdom. They are also called “tags”.
Assets can often also be intermediate steps between kingdom Attribute tiers. A road network doesn’t by itself turn a Territory 1 kingdom into a Territory 2 kingdom, but it’s an important milestone along the way. As discussed in Kingdom Improvement, when you’ve collected enough assets related to a given Attribute, you can cash them in to increase that Attribute permanently.
In general, assets give a +1 to kingdom actions that involve the asset. Some may give a +2, but only in a very narrow set of circumstances. A very few may give a +3, but only in extremely specific circumstances and are only usable once. Other assets or tags are negative. These cancel out positive tags on a 1:1 basis.
Multiple assets are not cumulative linearly. A single asset provides its normal bonus. To provide a second bonus requires two more assets (use the highest), a third three more, etc. For example:
A kingdom has a two +2 assets, and one +1 asset, and the party wishes to use all of them for one big bonus. First, the party weaves a logical narrative about how all these assets are being used. Then the party uses one of the assets for it’s first bonus, and chooses the +2. Then the party uses the two remaining assets (a +2 and a +1) for its second bonus, and gets the higher of the two for the bonus. The party therefore gets (2) + (2|1) = +4 to the check.
More importantly, advantages also represent narrative modifiers. A big stone wall means not only does your kingdom get a bonus to defense rolls, but it also means that if the kingdom is attacked, the PCs get to fight from behind a big ol’ stone wall!
See also: Kingdom Temporary Bonuses