In a standard, unmodded version of Counter-Strike 1.6, there is no official file strictly named "core.dll" required for the game to run—typical core libraries include files like engine.dll or client.dll .
Many legacy cheats use a file named core.dll as a custom-written library that contains the actual cheat code (like aimbots or ESP). Cheat Cs 1.6 Core.dll Download
Some "fixes" or "patches" claim to modify hitboxes or recoil by replacing original game files with a custom core.dll . Common Features of CS 1.6 DLL Cheats In a standard, unmodded version of Counter-Strike 1