In this guide, you will come to know how to unlock The Battle Pass in Diablo Immortal.
First, you have to make it to Ashford cemetery which is the second place. Then you have to do the mad king’s breach in a dungeon and get to Ashford manner. The lord’s rest is also part of the dungeon.
If you follow the story definitely, you will unlock it. After this, the battle pass will be unlocked.
Then you can claim your rewards which will give you the experience of the battle pass and you can start getting rewards for the battle points.
Battle points are basically battle pass currency that you will get through ding your code x adventures and guides.
After that, go back to the main menu and click on the battle pass on the top left. From there, you can claim your rewards. 
If you buy the empowered one, you will get a rank up as you get a weapon cosmetic. You will get a ghost armor when you reach rank 40. It will also change the portal. The portal will look different from the normal portal. So mostly you will see the cosmetic staff and extra crafting stuff.
In the rank-up menu, you have to spend the real currency, in case you want to level up faster. You will get more of these as you unlock more areas.
