Shadow Plums are items that, when eaten, permanently increase your max stamina by five. They can be found in a variety of different ways, including exploring the town and mining.
- In a chest in the trees near the top left of the map.
- On floor 30 of the mine, inside a chest.
- Fiona, Emily, Kain and Renesco's third friendship reward.
- The Mayor's second friendship reward.
- Give Denny's sword to Denny.
No villager will accept a Shadow Plum as a gift, and they will simply hand it back to you.