The absence of gods
It seems, when a god goes missing, at least one of the items in their portfolios, maybe the most important piece, is affected negatively. The other gods seem to be able to compensate given enough time, but in some cases this has not happened yet. Maybe they dont care as much as we’d like to think.
- The death of Librus - God of Legacy, led to the The Curse of Illiteracy. Dooming the Elven Empire.
- The Death of Death - Trapped souls on the material plane.
- Sol - God of Hope’s temporary leave, caused the Night Century
- The Fracture of Wedn causes certain types of Unstable Magics.
Powers from missing gods
Clerics or priests of missing gods are not granted their magics from them. They may however gain powers from sympathetic gods, demi-gods or other powers in the world. The works of the gods, or results from them, dont disappear from the world however.
Conclusion
If gods missing can cause their portfolios to suffer, bringing them back might fix their domains. Or maybe other gods rising may be able to take over them. Loosing more gods would probably entail bad things happening to the world.