Callan chose these blades because he was good with them and he loved using his fire powers with it.
But one day Callan's overconfidence got him captured by the evil half-Makuta, Attakrahnus. His blades were taken and upgraded by an evil little minion named Rogi. But Callan was soon rescued and his even better blades were returned to him. His blades now automatically absorb the element channeled through it and can use it no matter who is using it. For example, if Gali channeled her water powers through it, Callan could shoot water out too. However, it can only absorb so much, which means the element powers could run out. Which is why Callan is trying his best to save the power for when he really needs it.