Plague / Epidemic
Although the Seelie fey had now resettled themselves firmly in the living forest, they now began displaying symptoms of sickness and lifelessness. The illness did not spread to anyone not from the Faewild except for the gnomes. This led scholars to quickly discover that it was caused by no longer having a link to the Faewild.
Due to the victory of the Unseelie fey, it was no longer possible for the Seelie court to access the portal from which they came. Similarly, all communication with them was shut off and the Seelie fey were left with no way to return to the Faewild or get rid of their sickness.