As the players continue, I was thinking of adding more difficult random encounters, perhaps hinting at... something. The nature of Strahd or the realm shifting, Strahd coming undone as he's watching these adventurers affecting his world. I don't precisely know. I thought of throwing in sorrowsworn, stronger undead, perhaps larger beasts. Maybe some undead mind flayers. I'm not sure. All to accomplish two things: a greater challenge, and to hint at something greater to come.

Next, a potential "Nightmare mode".

Strahd strikes me as a being that's insane and unhinged, yet seems very put together. I wonder if, as the players slowly unravel his world and undoes his plans, he would slowly come undone. As he does, his manifestation of the world fades (like the shell people), and they either begin madly shifting into horrendous entities (sorrowsworn), or perhaps it's the full weight of the Shadowfell and Negative plane pressing in, creating manifestations to arise against Strahd's will.

An alternative explanation could be that the Dark Powers are mocking Strahd for his weakness and making him painfully aware if his situation, forming nightmarish things in the realm that oppose both Strahd and the characters.

Thoughts?