Ads keep the MarioWiki independent and free :)
In Adventure Mode, Bask Ruins is the first area visited. When Mario and Toad reach here, Dry Bones claims that Bask Ruins can only be entered by those who can play tennis, and teaches the basic tennis rules to the player while playing with him before challenging Mario to a proper match. After Mario wins, he and Toad are permitted to enter the Temple of Bask. Inside the temple, Mario encounters the temple's guardian, Aster, who gives Mario some background about Lucien and asks him to find the five Power Stones to prevent Lucien from regaining its full power. Aster then teaches Mario various techniques such as the Zone Shot and the Special Shot. Once the tutorial is over, Aster tells Mario where to find the Power Stones.
Later, after Mario, Peach, and Daisy defeat Lucien's puppets at Marina Stadium, Bowser steals Lucien and the five Power Stones and brings them back to Bask Ruins, where he uses them to transform into Bowcien. Mario confronts Bowcien at the Temple of Bask Shrine, where he successfully defeats Bowcien and breaks Lucien with a Zone Shot.