All twelve Health Cells must be collected. The Forlorn Ruins contains one cell which must be collected before you free the wind, since this prevents you from returning later. The remaining eleven cells are in the open area and can be found at any time before you enter Mount Horu. Some will not become available until you have certain skills. All will become available after you have the Charge Jump skill. There is an ability which shows cell locations on the map, however some may be hidden in secret areas.