Update v1.15:
Fixed a problem that allowed invading hosts mid-boss battle by performing specific operations
Change of name and description of magic “Pestilent mercury“

Run setup.exe and install update
Copy crack from CODEX dir to installdir
Play

This patch requires:

Dark.Souls.III.The.Ringed.City-CODEX
Dark.Souls.III.The.Ringed.City.Update.v1.13-CODEX
Dark.Souls.III.The.Ringed.City.Update.v1.14-CODEX

General Notes:

Block the game's exe in your firewall to prevent the game from
trying to go online
If you install games to your systemdrive, it may be necessary
to run this game with admin privileges instead