This is Rio Bakura's spirit, 5000 (in the Japanese episodes 3000) years ago. Bakura is the sole survivor of his village - Kuruelna. The little boy sees with his own eyes how Aknadin's army massacres the whole village and from this moment on, he concieves a hatred for the Pharaoh, the priests and the whole kingdom. Bakura becomes a great thief so he can rob the Pharaoh's treasures, mostly the Millenium Elements.
We can tell for sure that Bakura the Thief is just a pawn to Bakura (the one who is known in the first seasons as the Spirit of the Millenium Ring). The Thief's objective was to collect all Millenium Elements so the Great Zork Necrophidius (in Japanese 闇の支配者 ゾーク Zōku, the real identity of the Spirit of the Ring) can be awaken. With his might and powerful KA - Diabound, even the Egyptian Gods would not be able to win.
Translated from Bulgarian language by: Ted^Maverick (TV_Squad)