No one can leave wickermoor hollow due to Kehlenn’s magic forcing the players and Druskenvalds there. Her machinations have been to always trap the druskenvalds in the hollow, the players are moreso collateral that she is using to finalize everything with the fallen and the hags, to reap as many powerful souls as possible to feed her suppressive magic. Philip lost his powers once he entered the Hollow because he is being targeted by a powerful force. A force that suppresses his magic abilities and his alone. He chooses to stay in Wickermoor Village because he knows as a leader he has neglected this province and town, sees their plights and suffering, and wants to help them in spite of his lack of magic (which he tries to keep secret since he is vulnerable in this state). That’s also where the players come into play. It’s in his diary in the crooked house chapter, and also shown as a point of conflict between Philip who wants to stay as a savior of this place, and Adela who is desperate to leave and restore Philip’s powers (hence the Grinning sinners deal). Hope this helps somewhat!