Here you can buy the key Crusader Kings II The Old Gods DLC (addition to Crusader Kings 2) at a bargain price. After purchase, you will immediately receive a key, by activating which you will add DLC to the game Crusader Kings II to your steam account.
Without the original Crusader Kings 2 II game on your account, you cannot activate the The Old Gods DLC add-on.
https://store.steampowered.com/app/210908/Expansion__Crusader_Kings_II_The_Old_Gods/
You can activate the key in any region.
Steam