Pierro is the very first member of the Fatui, thereby the first of the Harbingers. He has personally recruited several Harbingers, including Dottore, Pantalone, Signora, and an unknown Harbinger (likely Scaramouche).
Pierro's past is largely a mystery, but is alluded to in Mocking Mask. He failed to gain favor with the past ruler of an unknown country due to being less capable than the other sages,[Note 1] and could not stop them from doing something that tore away the "veil of sin," which brought destruction to the country (likely Khaenri'ah). For this reason, he became embittered with the "divine" and joined the Tsaritsa's cause.
At some point in the past, Pierro went to Sumeru Academia in pursuit of rumors surrounding a student there performing heretical acts. He found the man who would become known as Dottore, who readily agreed to join the Fatui Harbingers upon discovering that they were supportive of his efforts to create an enhanced human who could surpass the gods.
Pierro also recruited Signora, at the time known as the Crimson Witch of Flames, to join the Fatui. He bestowed her with a Cryo Delusion in order to suppress the intense flames flowing through her body.
Pierro is also mentioned towards the end of the event Unreconciled Stars. While investigating the meteorite core at Musk Reef in Where Ancient Stars Align, fellow Harbinger Scaramouche indicates that Pierro deliberately sent him to Liyue knowing he would encounter the meteorites and make a discovery: "The stars, the sky... It's all a gigantic hoax. A lie." Irritated that Pierro gave him no forewarning about what he would find, Scaramouche leaves, presumably to confront the senior Harbinger.
- In commedia dell'arte, a type of Italian theater, "Pierrot" is a sad clown, pining for love of Columbine, who usually breaks his heart and leaves him for Harlequin.
- Pierro's Chinese alias (丑角) literally translates to "The Clown Role," which is a direct translation of the role of Pierro (sad clown). It can also by extension mean The Jester, The Comedian, The Fool, or The Buffoon.
- Pierro was originally called "Pedrolino" in Tartaglia's Delusion Story. In Version 1.5, that mention of "Pedrolino" was changed to "the Jester," and the newly released Pale Flame set gave the Jester's name as Pierro.
- In the original Chinese description for Mocking Mask, the term translated as "sages" (Chinese: 贤者 "worthy, virtuous ones") is different from the one used to refer to Sumeru's sages (Chinese: 智者 "sages, wise men"). The term 贤者 was first used in a Chinese-only BBS post about the Eleven Fatui Harbingers.