Kasimir

Kasimir (a.k.a. The Lone Wolf) was a hermit living on the island of Kusho on Dominaria. His real name was Shasido Mayasi.

The Kentsu
Shasido used to be a general in the kentsu, but wanted to be the imperial champion instead. When that position became vacant, he was ordered by a higher general, who probably liked having a subordinate in such an important position, to travel to the Imperial Shrine and meet Tetsuo Umezawa, who also wanted the job. They dueled and Tetsuo was victorious. Shasido didn't want to live in disgrace and chose exile instead. Tetsuo promised to keep his name a secret within the Empire of Madara.

Defending Kusho
On Kusho, Kasimir allied himself with Gosta Dirk, a powerful warrior and wizard who acted as the island's leader in times of crisis. When Lady Caleria rallied the Edemi Islands against Madara, several counterattacks were made by the empire, and Kasimir acted as Kusho's guardian, even fighting Tetsuo again.

When the monsters and assassins that Ramses Overdark had sent couldn't conquer the Edemis, Emperor Nicol Bolas sent the kentsu to do it. Again Kasimir defended the island, but he was beaten in combat, by none other than Marhault Elsdragon, leading general of the kentsu. Kasimir was grievously wounded, for Elsdragon had blasted a hole through his torso. He survived nonetheless, thanks to the healing water of Kusho and Ragnar's healing abilities.

After that Kasimir was seen guarding Gosta, who had fallen ill after Halfdane poisoned the mana of Kusho. The hermit nearly killed himself fighting the shapeshifter, but again the healing waters saved him. The last time Kasimir appeared was when he brought Ayesha Tanaka and Tor Wauki the message that they should get off Kusho as soon as they had killed Halfdane. Presumably, he continued to be Kusho's greatest defender, and might have been part of the group Lady Caleria rallied to extract reparations from Madara.