Ryoku (リョク, Ryoku) is a boy from Shin village, East Asia. He met Black Star as he and Tsubaki were looking for Masamune. It appears that Ryokou and/or his village has had dealings with the Star Clan in the past, as he recognized the tattoo on Black Star's arm, but he may just know that from the clan's reputation. At first believing Black Star was part of the Star Clan, he offers him money to leave before chasing him out of the village for fear he may attack them. However, it was that fear and the fear of not being powerful enough which allowed him to be possessed by Masamune. After Masamune was defeated, Ryoku comes to realize Black Star was not a member of the Star Clan but that still didn't mean that he liked him anymore than before.
Eibon is an enigmatic sorcerer and former acquaintance, if not friend of Shinigami, who is revered for the creation of numerous Demon Tools, including Brew. As one of the eight Great Old Ones, his "wisdom" and very existence drives men to madness. Known as the "Great Sorcerer", he is the most powerful Sorcerer in the world, was part of the Eight Warlords, and was a former friend of Death himself. (Source: Soul Eater Wikia)
Referred to as "Mole Hunter" Joe Buttataki, Joe makes his first appearance at the end of chapter thirty-seven of the manga when he is called to Shibusen to investigate the possibility of a spy. His name when literally translated is "kick the shit out of," a phrase he says at the end of chapter thirty-seven in the manga. He is able to detect the snake placed in Marie's body. He is the ex-boyfriend of Marie Mjolnir. Joe had apparently kept his distance from her, fearing that his "soul perception" may grow so powerful that he could see through her. Joe stated to Marie that he regretted his decision and asked her out for dinner. He considers his ability unpleasant since it only allows him to work a job where he can only mistrust his allies. Joe is the first technician to be able to pierce a witch's technique to appear human and his power is growing even now. -Wiki
The big sister of the group. Wears bandages in a fashionable way. She controls the bandages freely, using them to attack and dress wounds. She carries a giant injection needle which contains a healing liquid. The group is very close to her and calls her "Mami-nee". In her younger days while she was escaping from her pursuers she came across James in lab. She helped the depressed thn nameless James find a purpose in life and the two developed a strong relationship. The four have been together since young and there was an event where Mamii saved Aki by giving her left eye in place of Aki's soul. but by the end of "first stage" she is seen to have recovered that eye. (Source: Wikipedia)
Type: Monster Race: Souleater The product of the egg the Tri Command was hatching. It also ate all of the Tri Command. A huge black wolf monster which looks similar to Aki's soul form. His first word is Aki's name. It was revealed in the last chapter of Second Stage that Bellze is a figure from Aki's past. Bellze was once a human Soulhunter and he took the souls of Aki's parents. He used the monster souls he collected and performed the secret technique of race change that turned to an egg form. With the souls the Tri Command collected Souleater Bellze emerged from the egg. (Source: Wikipedia)
The legendary sword used by heroes and kings. It has a great power that is unmatched by any other weapon. It turns out that anyone can use Excalibur. However, no one can put up with its personality (it has a bigger ego than Black Star). The only reason that those who use it are called heroes is that they can put up with its annoying habits, such as a list of one-thousand things he demands to be completed, such as daily five-hour reading sessions. Excalibur was first introduced when Kid and Black Star found a book about him and thus sought him out, only to discover that the book had in fact been written by Excalibur himself. They quickly ditched him due to his personality. His other form is completely the opposite given his elegant weapon form, looking like a cartoon-ish gentlemen with an outrageous mustache and no pants. On the other hand, his legendary powers have been proven by a fellow Shibusen student who found completing the appointed tasks easy. Excalibur can grant great power, light speed and teleportation, and the wielder can easily defeat three of Shibusen's strongest combined. In the end, Excalibur was put back again because the student could not put up with his annoying sneeze. His existence throughout the story is purely comical, with the exception of the fact of how he informed Kid, the Thompsons, Buttataki, and Blair about the story of Eibon, backed by Shinigami. (From Wikipedia)