Aster is the deteuragonist of the game Mario Tennis Aces for the Nintendo Switch. It is the guardian of the Kingdom of Bask. Aster serves as Mario's guide through story mode.
Aster is a dedicated guardian. He is devastated when Wario and Waluigi take the ancient racket, the Lucien, as he knew what it could do. Aster has made it his duty to make sure Lucien does not destroy the world. When Mario makes his way into the Temple of Bask, Aster allies with Mario and teaches him special tennis moves, such as the Special Shot and different types of shots.
While not much is known about his backstory, Aster was tasked by King Bask to guard the Temple of Bask, specifically to keep the Lucien's dark powers from getting stronger. Wario and Waluigi invade the temple, not knowing the Lucien's true powers, and take the racket, becoming its thralls as it awoke. Mario and his friends make their way to the temple, and Aster becomes their greatest ally.
Aster later gives Princess Peach and Princess Daisy the Special Shot to help them win the Lucien Cup's doubles phase when the Lucien starts the cup in the first place. However, King Bowser Koopa makes his way to the stadium and takes the Lucien, fusing his power with the racket to become the Bowcien.
Mario makes his way and with the help of Aster defeats Bowcien, destroying the Lucien in the process.
- It is not known what Aster looks like.