From about 1428, the Shaybanid Abu'l-Khayr Khan killed the Siberian Khan, Hajji Muhammad and established a brief empire that stretched from Sibir to the Syr Darya.

As people and power drifted southeast, the remaining Shaybanids coalesced around Ibak (Allworth, p. 47).

He appeared along the Volga claiming to have a better right to rule the Great Horde than Ahmed Khan (Howarth, p. 980).

At the time of the Ugra standoff Ibak may have has some arrangement with Moscow to threaten Ahmed in the rear.

In 1495 (most common), or 1494, or 1493 (Grosset, p. 489) Ibak was killed by Mamut, a grandson of Mar (Howarth, p. 981), who then became Khan of Sibir.