Both of these adventures seem to be worthless due to losses needed to complete them and poor rewards. Surely this could be reversed with adding a small chance of getting buildings from them.
Sons of the void = chance for silo
Secluded Experiments = chance for watermill
Since they are not quite as epic as the other buildings from adventures, there could be a higher chance ~10% and it would provide a source outside of gems to remove the mass rebuilding of wells/fields which annoys players.