Normally a good-natured man, as a commander he was full of confidence and dignity. He would also become a very close friend of fellow general Teo McDohl and was considered the second most experienced of the Great Generals behind Teo.
He is known as "Kasim of the Blue Moon" due to his Blue Moonlight sword. This curved blade scimitar was forged by Senan nomads using a long-lost technique of the Sindar. These people has since disappeared and the secrets of Kasim's sword have been lost to time. Originally from the northern wastes himself, Kasim was entrusted with overseeing the Senan region from Moravia as he was used to desert warfare.
During the early stages of the Gate Rune War, Kasim Hazil attempted to recall Mathiu Silverberg into the service of the Scarlet Moon Empire, but this attempt failed. Following the death of his good friend Teo McDohl, Kasim Hazil was assigned to guard the northern defenses and decided to build up his forces. Kasim also began to apply extreme pressure on the rebel factions within Senan.
A man of strong patriotism and loyalty, it was thought that Kasim Hazil would be impossible to convince to join the Toran Liberation Army. When the Liberation Army infiltrated Moravia and Mathiu manipulated the Jowston army into invading, Kasim was infuriated as a man who had spent his life protecting the north from Jowston.
Even though he knew Mathiu oppossed the empire, Kasim never thought their view of Jowston would differ so. However, he was ultimately convinced to stand down by Milich Oppenheimer, fighting for the Liberation Army for the remainder of the war. By doing so, Kasim hoped to confront the Emperor and convince him to change his ways.
Kasim served the Toran Liberation Army for the rest of the war. At Toran Castle he would be most frequently be seen in the outer towers along with his fellow Great Generals, perhaps feeling uncomfortable among the rebels. During the final battle, when Windy berated Barbarosa, Kasim would immediately leap to his defense, unwilling to forgive the woman who changed the man that he served faithfully, even as a member of the Liberation Army.
Following the formation of the Toran Republic, Kasim Hazil was offered the position of Commander-in-Chief of the Toran Republic army. However, he declined this position in order to once more guard the northern border with Jowston and because as a former Imperial General was worried about causing unnecessary problems by accepting the position.
Recruited automatically after plot events in Moravia.
At the beginning of the American version of Suikoden, Kasim Hazil is mistakenly referred to as "Lord Kasim Hazin."
Kasim's Ending in the original Japanese version of Suikoden was changed in translation to the English language version; in the English version, he accepts the position of Commander-in-Chief conflicting with Kwanda Rosman who also accepts the position in his ending, but in the Japanese version, he turns this position down in order to return to Moravia.
An event where Kasim would cut down the infiltrating Kasumi with a single blow was originally planned but never implemented.