A mystical new friend you met in a mysterious new world. You found Elfilin as he was trying to save the Waddle Dees from the Beast Pack. He seems happy to be Kirby's guide, sharing helpful advice to save the Waddle Dees and rebuild their town. Thanks, Elfilin!
— Elfilin's figure description from Kirby and the Forgotten Land
Elfilin is a character who appears in Kirby and the Forgotten Land, serving as Kirby's primary companion. He is a small flying chinchilla-like creature capable of speech with giant ears, the right one having a large missing section on the rim, and turquoise fur. His eyes are bright blue and appear to shimmer in the light. He joins Kirby after being rescued from a Beast Pack cage in the stage Point of Arrival, hoping to help him save all the Waddle Dees, who Elfilin had gotten to know before they were captured. Later on, it is revealed that Elfilin was derived from a primordial life-form known to the new world civilization as "ID-F86", who seeks to be reunited with him to reform the ultimate life-form: Fecto Elfilis.
Elfilin's name is a corruption of his ID, "F87," as a result of splitting off of F86. It is also an anagram for "Nil Life"; "Nil" is the Japanese name for Void. The opening cutscene of Lab Discovera contains Morse code that spells "EFILLIN" when decoded; "Efillin" is "Nil Life" spelled backwards, and more similar to his Japanese name. In the Japanese version of Leongar's figure description, it is also revealed that his full name is "Fecto Elfilin" (フェクト・エフィリン), matching with Fecto Elfilis.
Through his actions and dialogue, Elfilin is characterized as a kind and energetic, yet unassuming creature who only wishes to live in peace with the Waddle Dees in the new world. When the Waddle Dees are captured, Elfilin is eager to rescue them on his own, but decides to let Kirby take the lead once he offers to help. Despite being imbued with incredible power, Elfilin seems to be unaware of this until after merging and re-separating from his other half; up to that point, he is largely helpless without Kirby's protection. Even after this, he states that his power is still weak, as he can only open and close a single portal to Popstar at a time.
Elfilin is critical to the story of Kirby and the Forgotten Land, since his capture and reabsorption into ID-F86 is the goal of the Beast Pack's leader Leongar, who is being possessed by Fecto Forgo directly. When Kirby defeats King Dedede at the end of Winter Horns, Dedede manages to sneak up from behind while Kirby is dancing and capture Elfilin for this purpose. When Kirby eventually catches up to them at Lab Discovera, he does his best to fight off both Leongar and Fecto Forgo to save Elfilin, but he is absorbed anyways. The two beings combine together to form the final boss of the game: Fecto Elfilis. Kirby has to battle this ultimate life-form until they are weak enough to the point where Kirby can separate Elfilin from them using Dome Mouth. From there, Elfilin helps Kirby destroy Fecto Elfilis for good by powering up his Big-Rig Mouth transformation. Elfilin uses up the last of his power to stop Popstar from crashing into the New World, but is saved from this otherwise-sacrificial act off-screen by Clawroline. He repays the favor to Clawroline by traveling with Kirby into Isolated Isles: Forgo Dreams to recover the lost pieces of Leon's soul and bring the lion back to life. Lastly, when Kirby defeats Chaos Elfilis in the final cup of the Colosseum, the last remnants of Fecto Forgo dissipate into a benign life force that reunites peaceably with Elfilin, ending the split for good.
The large hole on the outer rim of Elfilin's right ear is reminiscent of the practice of ear punching, wherein laboratory mice have specific sections of their ears punched out in order for researchers to more easily identify them.