Hi there!
TL;DR: Just like we counter the doomsday counter with magic, we should be able to reduce our threat level actively by diplomacy, quest - or passively by losing battles, units, cities, outposts, shards and so on.
Is the SK storming your last city like it was built out of shard bricks? Why not offer the SK a cookie along with an apology and tons of promises to be better in the near future
Of course this should be designed in a way that you can not do this many times, obviously. Some sort of cost increase and effectiveness decrease in proportion to the number of times you used this diplomatic approach. Diminishing returns.
And a quest that might pop up that leads to the result of lowering your threat would be nice and could fit nicely into the dungeon/game master mechanic (forgot how you call it exactly sorry).
Also, every time you lose a battle, lose an unit and lose any assets on the world map like outposts, shards, cities - your threat level should automatically decrease.
Help the dark master and glorious king of all sorcerers to return to the really important matters at hand, you know - renovating the torture chamber, walking the warg, shards.
Thank you 