Increase / Decrease
Increase and Decrease effects add or remove Bonus Value from an attribute.
Unlike modifying the Base Value directly, Bonus Values are tracked separately — the Player can inspect any attribute and see exactly where each modifier comes from (e.g. "Strength has a +1 from the Dwarf racial effect").
Stacking
Multiple Increase/Decrease effects on the same attribute stack with each other.
Each one is tracked independently, and the attribute's total reflects all active bonuses.
Reversibility
When the source of an Increase or Decrease effect is removed (e.g. unequipping an item, removing a class), the corresponding Bonus Value is cleanly reverted, and the attribute's total updates automatically.
Attribute Groups
Instead of targeting a single attribute, an Increase/Decrease effect can target an Attribute Group (e.g. "Skills").
When targeting a group, the Player is prompted to choose one or more attributes from that group to apply the effect to.
Info
All effects support multiple choices — the Creator can configure how many attributes the Player picks. When targeting an Attribute Group, the default is a choice of any attribute within that group.
Limitations
Increase/Decrease effects cannot target Attribute Inputs (such as a skill's Proficiency toggle).
Because inputs often have a constrained value range (e.g. 0–2), allowing bonus stacking on them could produce invalid states. Use a Set effect to modify inputs instead.