Custom enchantment books have a success percentage. This is the chance that is will successfully enchant the item. If the enchant fails, it will destroy the item. To prevent the item from being destroyed by a failed enchant you need to either put a white scroll onto the item or use magic dust to increase the success percentage of the custom enchantment book to 100% so that it cannot fail.
How to obtain
You can use exp or tokens to obtain custom enchantment books. To open the custom enchants menu use the /ce command. This will allow you to buy books with exp. To buy books with tokens use the /voteshop command and go to the custom enchantments section.
You can obtain white scrolls from the enchantment section in the vote shop. Access the vote shop with the /voteshop command. White scrolls protect an item from being destroyed by a failed enchantment.
Magic dust is used to increase the success percentage of a book. Magic dusts come in different tiers just like the custom enchantments. You need to make sure the custom enchant book tier and magic dust tier are the same to be able to increase the success of a book. Example: you need to use legendary magic dust on a legendary custom enchantment book.
Removes a random enchantment from an item and gives you the book.