You can haggle: 75% chance the price drops to 4, 25% chance it goes up to 7. Only on Witch Marsh, Glyph Ruins, Serpent Basin, Golem Home, Abandoned Quarry, Boneyard Bog and Scorched Hill.
Golem: combine two copies of the same Common or Golden item. Large Golem (sometimes): upgrade an item to Golden, or a Golden item to Diamond.
Lushwood Grove
No enemies
Fairy: turn an item into another item of the same rarity. Lush Chest: choose one of four Common items. 1/100 chance that they are Golden. Beehive (sometimes): get a Honeycomb, which can be combined with food at a Cauldron. Guarded by Honey Bees.
Large Bonfire: rest here at night to skip to the next day and restore all health. Woodcutter: combine two items into a random Heroic item. At most one per map.
Trash Heap: holds 3 items of random rarity that you skipped in earlier chests. Junksmith: make a copy of a non-unique item. Only appears after you have skipped about 15 items from chests.
Wishing Well: make a wish. Choose one of three boons that improve other locations for the rest of the run.
Woolcrest Hills
Shepherd: adds another backpack slot.
Goldmane Shore
Golden Pig: catch it for a gold boon. Catching it also completes the challenge Ham Sandwich. The rarest island, and a large one with no Treasure Chests.