The Secretary of the Yuehai Pavilion is a Cryo character and before unleashing her might on the enemy you will first need to upgrade the character a little. Here is the complete list of the materials needed for Ganyu.
Ganyu Ascension Materials
Ganyu Talents Upgrade Materials List
If you're looking to upgrade your Mona here is the complete list of the materials you'll have to farm to Ascend the character and her talents.
