The black lion was given to Lai instead of the White Tiger because the latter was already reserved for Rei. Its element is mostly lightning too, but his attacks are mostly dark purple or black. In a sense, Galeon could be compared to Driger/Byakko as its opposite.
Galeon is probably a Holy Beast that was passed down from generation to generation within the Bai Hu clan.
In general, it feeds off Lai's quick temper to attack their opponents. However, Lai is often the one who has to put an end to their strategy due to his health or the other blader's quiet attitude.