The Fens have a length of 3 levels, a scaling level range of 1 to 5, and a material tier range of 1 to 2 (becoming 3 to 4 after returning from the East).
The layout is swampy, with dense, highly random trees on a background of shallow water and occasional grassy islands. The Fens are inhabited by nagas -- few in number, but fairly strong.
The Fens do not have a boss, per se. Rather, there is a portal on the third level. Touching the portal "destroys" it, and the resulting destructive energy sends the player (and the boss, who was hiding nearby...) to level 2 of a random starting zone in Maj'Eyal (one of Trollmire, Ruins of Kor'Pul, Scintillating Caves, Rhaloren Camp, Norgos' Lair or Heart of the Gloom).