To get Rainmaking Ritual Leftovers, you will need to increase your Rapport with Thunder the Shaman in the Nomad camp in Saland Hill. You will need to get to the Rapport to Trusted, which is level four, before she gifts you this item. Once you have it, right-click on the item within your inventory, and it will be added to your Adventurer Tome.
How to increase Rapport with Thunder in Lost Ark
To increase Rapport with Thunder in Lost Ark, you can give her gifts, perform emotes, play music, and complete quests. As you increase your Rapport with her, she will give you gifts. Eventually, she will give you Rainmaking Ritual Leftovers, the cooking collectible needed for the Adventurer's Tome.
To claim the Rainmaking Ritual Leftovers, you need to go down to Adventure on the bottom-right bar, then click on Rapport. Or click Alt + N. Click on Yudia, then press Claim Reward or the Magnifying Glass in the corner, then press Claim Reward under Trusted.
You can check your Rapport with Thunder by speaking to her. It will be at the top of the screen. It will take some time to increase your Rapport to level four. Check back each day to see if you give her any gifts or perform other actions.
For more guides on Lost Ark, check out How to craft Dawntree Sprout Cider in Lost Ark and All Mokoko Seeds locations in Prideholme in Lost Ark on Pro Game Guides.