Yes I defeated the boss then immediately returned and purified the area after, I returned to town and slept. Then got attacked by the assassin and then slept til dusk. Talked to Innis got told about needing another oak. And now have scoured the map looking for one. I already got the ones located just outside of the village and the one by the druid's forest area. It seems the Oak that is east of the swamp is missing?