Undead land of Imaru the Soul-Eater (power level 5), entered by soul rifting.
Getting in
Complete Dragon Slayer and start Withering Heights; you enter Fellhollow through the Forgotten Temple by soul rifting.
Fellhollow is a power level 5 region in Ashenfall, ruled over by Imaru, the Soul-Eater. The region includes underground spaces and is infested with all manner of undead monsters. Death will make an appearance in this region. Players will need to complete Dragon Slayer and have partially started Withering Heights to access Fellhollow. When players are first introduced to Fellhollow, they are greeted by Death in the Forgotten Temple and are then asked to meet Postie Pete, who will then explain that the way to get into Fellhollow is through soul rifting. This mechanic allows the player to enter spectral doors and gain access to new areas of the map that cannot be normally traversed.
Source: Fellhollow on the RuneScape: Dragonwilds Wiki · CC BY-NC-SA 3.0
Source: Guide for new players on the RuneScape: Dragonwilds Wiki · CC BY-NC-SA 3.0
Source: Woodcutting training on the RuneScape: Dragonwilds Wiki · CC BY-NC-SA 3.0
Source: Quests on the RuneScape: Dragonwilds Wiki · CC BY-NC-SA 3.0