The D.A.R.C.I. Catalyst is the one associated with DSC/raid-style exotic catalyst chatter, and its listed effect is a stability boost of 18. It’s described as a random drop from defeating non-Guardian enemies anywhere, not as something that drops only from Deep Stone Crypt specifically.

What it does

  • Increases DARCI’s stability by 18.
  • Once obtained, it needs 300 precision kills to complete.

Drop source

  • Random drop from non-Guardian enemies anywhere in the game.
  • It is not tied to a specific boss or activity completion in the source I found.

Note on naming

If by “DSC” you meant Deep Stone Crypt , there isn’t a single catalyst that’s universally known as “the DSC catalyst” in the source I checked; the catalyst information that matched your wording was for D.A.R.C.I..