His title prior to this was Irkin (Chinese: 俟斤; pinyin: Yijīn), meaning he was a tribal leader.
According to, Book of Sui, Heshana Khan was collecting excessive taxes from the Tiele, leading to resentment among tribes.
The Tiele thereafter rebelled and enthroned Irkin Geleng (Chinese: 俟斤歌楞; pinyin: Yijīn Gēléng), the chieftain of the Qibi (契苾) as the Yiwuzhenmohe Khan (易勿真莫賀可汗), who formed his power base aroud Bogda Shan.
His power was centered around north of the Yanmo Mountain (Chinese: 燕末山; pinyin: Yànmò Shān, near modern Emin County, China).
[4] According to Book of Sui, both Geleng and Yishibo renounced their khan titles as part of the submission.