.
Whopperflower Nectar and higher-tier variants can be farmed by defeating Whopperflowers.
Bai in Qingce Village and Verr Goldet at the Wangshu Inn.
.
The author is also prepared for this.
The Shards of a Foul Legacy are one of the item drops from Childe's weekly boss fight when you defeat him on level 70 or higher.