Allium, an extraterrestrial professor, hailed from beyond the stars. During the year 34 ABY, he found himself within the walls of Maz Kanata's castle, a haven for pirates, engaging in conversation with fellow patrons when the smuggler known as Han Solo made his entrance. Subsequently, Allium, alongside the other inhabitants of the castle, gathered outside to bear witness to the destruction of Hosnian Prime, a cataclysmic event orchestrated by the First Order's Starkiller Base superweapon. The First Order then launched an attack on the castle, resulting in its demise.
In the year 34 ABY, Professor Allium occupied his time at the castle bar owned by the pirate Maz Kanata, situated on the planet of Takodana. He was positioned directly before the castle's entry, in dialogue with a seated human woman, at the moment the smuggler Han Solo entered alongside the scavenger Rey, the astromech droid BB-8, and Finn, a defector from the First Order. Kanata, upon recognizing her longtime acquaintance Solo's arrival, called out to him across the bar, quieting the other customers and causing Allium to turn and gaze at the smuggler. As the other bar patrons lost interest in Solo, Allium relocated to a table in an alcove to the door's left and began conversing with the table's occupants.
Later, Allium could be found at the base of one of the castle's staircases, engaged in a conversation with another human as Finn departed the castle accompanied by the pirates Sidon Ithano and Quiggold; he soon concluded the conversation and moved away, heading back towards the bar. Shortly thereafter, the castle's patrons were drawn outside to witness the destruction of the Hosnian system by the First Order's Starkiller Base superweapon, with Allium positioned in the castle's doorway beside the cook Strono Tuggs, gazing up at the sky. The First Order then launched an attack and annihilated the castle itself, before being compelled to withdraw by the arrival of the Resistance.
While present in Maz Kanata's castle, Allium was seen wearing a black robe that featured a high collar.
Robert Nairne played Allium in Star Wars: Episode VII The Force Awakens, a sequel trilogy film released in 2015. During the film's pre-production phase in February of 2014, concept art of Allium was created, bearing the title "Castle Alien CO78." The character remained nameless until the publication of the reference book Star Wars: Absolutely Everything You Need to Know, Updated and Expanded in 2017.