After you have defeated the first boss ‘Eikthyr’, your next objective is to reach the Black Forest in search of the Elder. Unfortunately the location of Black Forest is not marked in the map and also all the maps are different so I cannot point a location on the map to show where the Black Forest is. Although there is a simple trick which will help you find the black forest.
When the game starts a bird will carry you into the forest. The location from where the bird starts is Black Forest. The flight path leaves an elongated trail on the map (See Below Pic). Follow back the trail on the map to reach the Black Forest.
Name of Biome appears on the top right corner of the map (See Below Picture)