In the Faerie Woods, there is a gate to the land of Under-The-Hill. A magical containment field of immense power permeates Under-The-Hill, one that appears to be strong enough to encase anything short of a god. The field is very selective, however, and tuned to a specific individual.
This person, known as the Fey Lord, is the master of Under-The-Hill. His power extends indirectly through his minions to the Faerie Woods as a whole. More information on the Fey Lord will be forthcoming after the Faerie Woods adventure is complete.
The Fey Lord is a Leshay who was trapped in ages long past. As a result of events in The Faerie Woods, the containment field has been damaged. Whether this means this being of epic power could escape his prison within decades or whether the damaged field can still hold him for eons is as yet undetermined. In either case, the Fey Lord hopes to come across other artifacts (minor, such as he obtained in the Faerie Woods, or otherwise) to speed his release.
Under-The-Hill is an extra-planar location (a demiplane of finite size.) Time flows strangely between Under-The-Hill and En World, and whether time flows faster or slower may be under the control of the Fey Lord.
The magical power holding the Fey Lord in Under-the-Hill is truly ancient, and predates the wards placed on some of the more troublesome lesser fey by a vast amount of time. While the greater may have inspired the lesser, they otherwise have no relation.