From this guide page to Dungeons & Dragons Dark Alliance you will learn how to unlock and activate the skin for the Lich Weapon.
In two editions of the game D&D Dark Alliance (Digital Deluxe Edition and Steelbook Edition) players can find additional content, namely the Lich Weapon set. It should be noted here that this is not a set of items (weapons), but skins.
The Lich Weapon Set skins in D&D Dark Alliance can be applied to a weapon other than the standard one, so they won't be available from the very beginning of the game. After you have acquired a new weapon (other than the original one), go to a merchant and change the appearance of your weapon.
Lich Weapon Set skins can be picked up from the Microsoft Store (for Xbox and Windows 10 PC users), PlayStation Store (for PS4 and PS5 users), and through Steam keys provided for Steam users.