Stormcrown has good synergy with Krul in general; it works for both crystal and weapon. It gives him health and cool down which are both bonuses for his a ability and the damage you get early game from each basic attack really helps get you into the late game and make him not as much of a potato early. In short, it gives you nearly the same damage a weapon item would but also gives you the utility you need to not be a glass cannon. Does this help?