Condition Stacking
Conditions don't stack except [[compendium:condition:Exhaustion]] (which has 6 cumulative levels). Multiple sources track duration independently.
In general, multiple instances of the same condition do not stack. If a creature is already frightened and a second effect would also impose the frightened condition, the creature is still just frightened — the effects don't compound.
The exception — Exhaustion: Exhaustion is the only condition that explicitly stacks. Each additional source of exhaustion adds another level (up to 6, which causes death). All other conditions are binary: you either have them or you don't.
Duration tracking: When a creature has the same condition from multiple sources, each source tracks its own duration independently. The condition persists until ALL sources have ended. For example, if two spells both impose the frightened condition with different durations, the creature remains frightened until both spells have ended or been dispelled.
Advantage/disadvantage don't stack: Similarly, multiple sources of advantage don't give "double advantage" — you still roll two dice and take the higher. The same applies to disadvantage. If you have both advantage and disadvantage from any number of sources, they cancel out and you roll normally.