God Catching Alchemy Meister:Quest 23

Making an Earthman
After you've cleared the Preliminary Training Ground (一陣の訓練地), heading back to the workshop will have Will thinking about the earthmen you fought while there. Thinking one might be useful, he calls on Serawi, who agrees to help him construct one of his own. Although she will take care of contacting an earth spirit, Will will still need to transmute a summoning stone to anchor it.

The recipe for the Earth Elemental Summoning Stone (土精召喚石) will be unlocked. Simply synthesize it to finish the request:
 * 3x Fresh Mud (新鮮な泥)
 * 1x Ground Earth (研磨した土塊)
 * 3x Magic Sand (魔法の砂)

Rewards

 * Aht will join you after this request is complete.