Keith (キース, Kīsu) in the Japanese version) and Berun (ベルン, Berun) are antagonists in the story, and members of the Faudo cult. They are voiced by Kenyu Horiuchi and Satoshi Taki, respectively.
Keith is one of the most eccentric mamodo seen in the series. Like all the competitors is the current battle, he is young, although he smokes a cigar and has a low voice. He often makes his entrances singing a gibberish version of Ludwig van Beethoven's Ode to Joy (while normally being blasted halfway through the song) and is also quite proud of it as he has a comical singing contest with Kanchome and Folgore's "Iron Man Folgore" song. He carries a walking stick that doubles as a baton, which he tends to wave about randomly while he sings.
Keith is very proud of his power, and once thought that he could count himself in the same league as the Four Mamodo Prodigies, who only the adult mamodo could defeat. His defeat at the hands of Vincent Bari disabused him of this, and he considered Bari his rival from then on.
In the manga, his intention in allying with Riou is merely to take control of Faudo for himself, contributing his powerful Dioga Ginisudon spell to the effort to break Faudo's lock. In the anime, however, he was shown to be loyal to Riou.
Keith's most distinctive features are his arms, which are on springs. He can use these to ram his fists forward in a powerful punch, as well as to propel himself forward.
Like most of the Faudo arc bookkeepers, not much is known about Berun. He wears a red ball on his nose, similar to a clown, although when he is happy, it opens up into a flower. He is a filmmaker, as he has been seen making a documentary in the desert in the anime, carrying a clapperboard, and shouting "ACTION!" at seemingly random intervals. He outright confirms this to Keith in the manga.
As with many Faudo arc characters, Keith and Berun's role greatly differs between the anime and the manga.
Shortly after the lock on Faudo is broken, Riou and his partner Banikis are defeated by Zeno and Dufort, who Keith promptly switches his allegiance to. He seals the deal by accepting a power boost from Faudo, changing him into a taller and stronger form. Stationed on the third level of Faudo's neck, he was the final guardian of the Main Control Room in Faudo's brain. He begins his inevitable fight with Zatch's group by unleashing a cerberus-like body part of Faudo's, called Degosumia. What Keith did not plan on was the arrival of his old enemy Bari (who, it was revealed, used to beat Keith up when they were in school), who destroys Degosumia in one hit and proceeds to face down Keith himself.
Keith realizes that he has no chance against Bari, and tells Berun to kill himself so Faudo could convert the parts of his body into power for Keith. Berun is reasonably hesitant, but in the end settles on offering Faudo some of his nose hair, which upgrades Keith to an armored form complete with laser-shooting satellites. However, Bari is still far stronger, and uses his ultimate spell, Dioga Zonisudon, to destroy Keith' armor and burn his book. As Keith disappears, he activates a torrent of lasers to block the door to the next room, which Bari ultimately sacrifices himself to get everyone through. Before disappearing, though, Keith tells Bari that he probably wouldn't have wanted to use such a cruel device on his enemies but the power of "Godufa" had really changed him. He tells Bari that he was glad that they could battle in the end and adds that just this once, he will let him go because they were rivals, finally fading away. Keith is later seen helping Zatch with his final battle against Clear. One month after Zatch becomes king, Keith is shown to be enrolled in a tensed school, along with Tsaolon, Rodeaux and Bari, who still retains his injuries from his fight against Elzador.
Berun is seen again when he is evacuated out of Faudo and witnesses the giant mamodo's defeat at the hands of Zatch, Kiyo, Brago, and Sherry. He is later seen eating a potato tempura, possibly remembering Keith.
Keith's part is significantly simplified in the anime as opposed to the manga. In the anime, he also keeps watch on the third level of Faudo's neck but he does not get an upgrade nor does he report to Zeno, as Riou is defeated much later in the anime than the manga. The room he is stationed in is also very different. The main teams that battle him are Kanchome and Parco Folgore and Momon and Elle Chivas, who use their powers of trickery and illusion to keep him busy until, as in the manga, Bari and Gustav arrive. Unlike in the manga, both Keith and Bari survive, and are evacuated out of Faudo.