Explore the Black Desert Mobile world and complete your “Collection”. You can receive rewards and bonus attributes by completing Collections.
Once you defeat Boss: Kelcas, the 'Collection' feature will become available. You can check your Collection by going to the [Main Menu] - [Collection] tab.
In the [Collection] tab, you can read short descriptions for each collection and register items for various rewards.

You can check the Collection categories on the left. Press [View Collection] to see the required items and rewards for each collection.

collection will be lifted sequentially in the order of completion of the main Quest, which is the progress chart of the adventure.

 If you’ve acquired an item that can be registered for a collection, it will be shown in the [Alarm] (bell-shaped icon) tab. Go to the [Collection] tab and press [Register] to register it.

The item you’ve registered will be consumed and will not be returned. 

※ You cannot register items that are enhanced, equipped with a crystal, or locked.

※ If you have multiple items that you can register, press the [Auto Register] button for more convenient registration.

If you press the item that you don’t have, buttons such as [Decoration], [Purchase Item], [Craft Trade Goods] will appear detailing how to obtain them. Press the button and you will proceed to the location where you can acquire the certain item such as the Deco Workshop, Market, Blacksmith, etc.

Collections are bound to your Family. You can use your Collection and acquire rewards only once per Family. 

You can acquire rewards by completing each list and Collection. Once you complete a whole category of Collections you will receive a “Completion Reward”.