To beat the Boss of the Earth Temple, all you have to do is run to one of the light spots, and use your mirror shield to reflect the light onto Jalhalla's belly. You must then pick him up, using the power of the Power Bracelets and fling him into one of the spiked pillars around the room, which causes him to explode into a group of Poes, allowing Link to pick them off one by one or use the Hurricane Spin to kill many at a time(only if obtained at the time). Once all Poes are killed, the fight is over.