Rumble's abilities don't cost anything but generate 20 heat. When Rumble reaches 50 heat, he is in the "Danger Zone", causing all his basic spells to have additional effects. When Rumble reaches 100 heat he overheats, silencing himself for 6 seconds to cooldown completely and causing his physical attacks to deal an additional 20 + (5 x level) + (0.35 per ability power) magic damage for the duration. While not overheated, after 4 seconds of not using his basic abilities he will start losing heat at a rate of 5 every half second, and 2.5 seconds later at a rate of 10 every half second.