Dammon mentioned "magically infused coolant" could be the solution. There is a component for a Staff in game where if you gather all parts become a staff of frost.
I propose simpler solution, easier to implement with what already exist in the game:
Buff the item, but if you use the component to "fix" Karlach, you no longer can assemble it.
The buff must be significant which making the exchange worth it should they choose to "doom" Karlach to Avernus.
