Sulfurina Ryuu-san

Sulfurina is the name of the embodiment of the Emerald Green Spring (a hot spring that emits a deadly posionous gas consisting of hydrogen sulfide and sulfur dioxide) the group has to tread to retrieve sulfuric acid from the spring to make the aspirin to cure Ruri of her illness. Silver can be used to detect hydrogen sulfide to see where the posion gas is and to avoid it.