Tacitus mentions a pair of twin gods referred to as the Alcis and worshipped in Northern Europe, especially along the coast and possibly in Iceland. The Alcis are known only as the "sons of the sky gods." They may be associated with elks or stags. Tacitus also described the priests of the Naharvali tribe in effeminate costumes who worshipped the Alcis, but not enough is known about their worship to say if this was typical of all Celtic tribes or the norm only for the Naharvali.