This is something that would probably come into play later down the line but, after seeing how the Swarm tore apart the Unknown Passage, and how it is slowly getting stronger and attempting to break free....

My idea is a month-long event leading up to the core being released. There is a breach in the core, and slowly the Swarm is getting through and infecting the rest of the Clockworks.

The Shadow Lairs were only the beginning - in the first new gate of the event a couple stages in T3 have been deleted and replaced by ??? stages, random variants of the Unknown Passage scaled to being more inline with what average tier 3 players could reasonably expect to survive although still more challenging than normal T3 stages. Players who survive these passages are awarded CR/Heat/Materials/Sparks proportional to the challenge of the stage and also receive special new tokens.

As the event progresses, each new gate will be more tainted than that last. First a stage or two more have tainted in Tier 3, then nearly the whole of Tier 3 is infected and the infection has spread to Tier 2, then Tier 3 is completely infected and a new mini-boss stage appears with a "Swarmlargo" enemy with a higher reward and Tier 2 proceeds to be further infected. Finally, the breach is sealed and new fresh gates appear, and the Swarm gates are eventually cleaned.

During the event and for a few days afterward, players can redeem their tokens to receive new unique costume items - pure black wolver, demo man, magic, and gunslinger, with the eye color changed to match the swarm.