Aster

"I am Aster, humble guardian of the noble King Bask. It is my duty to watch over the one called Lucien."

- Aster

Aster is a guardian of the ancient Kingdom of Bask appearing in Mario Tennis Aces.

History
Not much is known about Aster's backstory, other than the fact that he was tasked by King Bask to guard the Temple of Bask as a spirit and keep Lucien's power in check. When Wario and Waluigi steal Lucien oblivious to its true powers, Aster asks Mario to recover the Power Stones before Lucien can and teaches him the Special Shot to help him.

Later on, when Lucien forces Mario to partake in the "Lucien Cup" in which the loser must hand over their Power Stones to the winner, Aster appears to give Peach and Daisy the power of the Special Shot to face the corrupted Wario and Waluigi. At the end of the Lucien Cup, Aster then begs Mario to stop Bowser in his new form, Bowcien.

After Bowcien is defeated, Aster thanks Mario for restoring peace to the Kingdom of Bask and the spirit of King Bask before vanishing. Starting in version 2.0.0, after Mario completes the Ruins of Trials, Aster tells him that he is "a true king of tennis" and asks him to use that power to preserve peace around the world.

Trivia

 * The Japanese name for Lucien transliterates to Aster's English and Spanish name.