Southern Ruins

Relic	Disassembly	Area
Bomb	Ancient Scroll Zettel	Sector Two Ruins Entrance
Craft	Pressed Oil	Sector Two Ruins Entrance
Healing Salve	Mixed Lubricant Distilled Water	Sector Two Ruins Entrance
Ice Bomb	Freezing Gas	Sector One Ruins Courtyard Crumbling Altar
Allgemein Board	Wood Chips	Sector One Ruins Courtyard Ruins Altar Crumbling Altar
Freezing Gas	Neutralizer-B	Sector One Ruins Courtyard Crumbling Altar
Spray	Distilled Water	Sector Three Ruins Altar
Cloth Scraps	Hand-Wound Thread	Sector Three Ruins Altar

Strong Monsters
Red Fang Returner (19) Mutant Breaker (7) Regen Breaker (25) Bloody Breaker (33) Rampaging Eye (21) Ultimate Eye (47) Blue Sky Monster (14) Dark Sky Monster (35) Crimson Silver Wolf (8) Ultimate Death Bug (15) Great Death Bug (49) Regen Rat (26) Mad Steel Beast (9) Manic Steel Beast (45) Ultimate Gaia (27) Mutant Lizardwing (13) Regen Lizardwing (37) Blue Elder Dragon (20)

Ruins Entrance

Items	Monsters	Field Effects
Paper Scraps Bird Egg Sea Bird Egg Phlogiston Paper Scraps (Rare) Sea Bird Egg (Rare) Ext. Bird Egg (Rare) Phlogiston (Rare)	Mini-Slag Guard Fake Ruin	Check relic Check collection sharing Check strong foe Check land change

Items	Monsters	Field Effects
Garden Stone Moss Grass Mountain Feather Eagle Feather Garden Stone (Rare) Moss Grass (Rare) Mountain Feather (Rare) Eagle Feather (Rare)	Mini-Slag Guard Fake Ruin	Check relic Check collection sharing Check strong foe Check rare materials

Items	Monsters	Field Effects
Phlogiston Aqua Light White Flower Red Flower White Salat (Rare) Aqua Light (Rare) Green Gemstone (Rare) White Flower (Rare)	Mini-Slag Fake Ruin Flatfish	Check relic Check collection sharing Check strong foe Check relic change

I have a lot more luck getting Dunkelheits at Lab of Eternity, but it is indeed possible to get them here.

Items	Monsters	Field Effects
Salat Fresh Salat Aqua Light Earth Stone Fresh Salat (Rare) White Salat (Rare) Earth Stone (Rare) Blue Gemstone (Rare) Dunkelheit (Max) Purple Flower (Max)	Mini-Slag Fake Ruin	Check relic Check collection sharing Check strong foe Check battle change

Requires some bombs/crafts to get past the boulder. Sometimes you may have to use more than one.

Items	Monsters	Field Effects
Pendelock Earth Stone White Flower Red Flower Pendelock (Rare) Sea Bird Egg (Rare) Ext. Bird Egg (Rare) White Flower (Rare)	Mini-Slag Guard Fake Ruin	Check relic Check collection sharing Check strong foe Check battle change

You can't enter here till Assignment 7.

Items	Monsters	Field Effects
Garden Stone Salat Fresh Salat Aqua Light Fresh Salat (Rare) White Salat (Rare) Aqua Light (Rare) Rouge Gemstone (Rare)	Watchman Flatfish Flounder	Check relic Check collection sharing Check strong foe Check land change

You can't enter here till Assignment 7.

There's also a boss here. THE boss. After beating it, you get a lithograph piece.

Items	Monsters	Field Effects
Paper Scraps Salat Fresh Salat Phlogiston Fresh Salat (Rare) White Salat (Rare) Phlogiston (Rare) White Flower (Rare)	Yellow Spirit Flatfish Flounder	Check relic Check collection sharing Check strong foe Check collection change