An NPC, a boss, the mother of the forest. A friendly NPC who can trade items with the player, just like the Pearl does.
- She is not awake in winter (or at night in any season).
- She catches fire in summer and dies. To avoid this, you can give her Tree Jam so that she grows a protection for herself (or an area for the player to make a base... maybe...).
- She respawns in spring if she dies in summer or in the hands of the players. If she is alive and cared for with Tree Jam (she only produces fruit in this season).
- She can be killed by the player in a boss fight, something similar to the Poison Birchnut Tree fight but harder. She becomes stronger if she was cared for with Tree Jam.
Regarding her trade shop, I have no idea what it could be, but you can give me ideas 
The idea was to create an NPC that can help you alive or dead, to give the player the choice, something similar to the idea behind the Antlion.