if you don have any strong magic/pyro to use on them, better use weapon with fire dmg. strategy wise, run around the outer side of the pillars to gain some distance with the fat one. he is slow and the pillars will block him from the rushing attack which is very damaging.... the slim guy will always get to you easily cos he has a dash attack from far range. when he do this, take a few whacks. keep an eye on fatboy while doing this, if he is near, run around again..... after the slim is dead, just attack fatboy in close range.... his swipe and hammer attacks wont hit u... u just have to look out for his charging electric slam when he floats up. hope this helps.