Tarn Aeluin ('Blue-mere' (Sind.)) also known as Aeluin was the name given by the grey-elves and the Edain to a small clear blue mountain lake in eastern Dorthonion in the centre of the highlands, at the entrance of the shallow pass which led to Ladros. It is said to have been hallowed by Melian the Maia. It was here that Barahir and his twelve comrades hid from Morgoth's forces after the Dagor Bragollach.