The name osmium is derived from the ancient Greek word osme meaning "smell". Apparently one of its oxides smells like radish. It is the element with the highest density. Belonging to the noble metals it is very unreactive. Because of its high melting point it was used in alloys with tungsten for light bulbs.
Rhenium was discovered in 1925 and named after the river Rhine – the home area of one of its discoverers (Walter Noddack, Ida Tacke and Otto Berg). This very rare element is mostly used in alloys.
Rheni the monster resembles the river god Rhenus – also called "Father Rhine".
This element was named after Tantalos, a character out of Greek mythology. Tantalos was a powerful king, who was punished by the gods for commiting several crimes. He was forced to stand in a lake up to his chin. But whenever he tried to drink from the water, it disappeared. Delicious fruits were hanging above him, but whenever he tried to reach for them to eat, they rose beyond his reach. This became the source of the English word tantalise.
The name of this element comes from the Latin word for Copenhagen "Hafnia", where it was discovered. There are only few very specific technical uses for hafnium.
The monster is inspired by the coat of arms of the city of Copenhagen.
Erbium is named after the swedish find spot Ytterby, just like Yttrium, Terbium and Ytterbium. Apparently the chemists of that time were not very creative in naming.
Therefore Erby is the third monster of the Ytterbies.
The name Holmium is derived from the Latin version of the city of Stockholm, because the element was discovered in Sweden. Therefore the moster design is inspired by the coat of arms of Stockholm: