Ooh, he'll go down the ventilation shaft.

It's pretty collapsed. Goes down quite a distance and then branches out horizontally. Gangs of rats squeeze thorough the cracks, always traveling in packs and moving simultaneously.

Huh! "Hello?" he tries, addressing the rats.

The pack issues a cacophony of squeaking and runs for cover in the nearest rubble pile. A few rat heads pop back out to observe.

He waves at observing rats.

One rat walks out into the open with a small black ball of something, sets it aside, then repeatedly mimes eating and then holding out its paws and then touching its weird piece of coal(?)

...he'll try holding out his hands?

Eating. Coal. Eating. Coal.

...is he supposed to take the coal? He will reach for it slowly.

SQUEAK SQUEAK SQUEAK!

Okay, he withdraws his hand then.

The rat takes its coal and retreats under the rubble pile with it. The watching rats vanish.

Huh.

He descends further into the mine and explores it.

Lots of collapsed tunnels. A few more rat packs that watch warily. The ruins of an equipment locker or possibly a pantry. An old, inoperative robot of some sort crushed in a dead end. The ruins of some sort of... Ore crusher? Something big and industrial anyway.

Gosh, a robot. He takes a photo of the robot. Investigates what's in the locker/pantry.

Lots of rat droppings mostly. Old hand tools and chewed-through rubber suits proportioned for a Dwarf and tiny scraps of plastic foil.

Neat.

Worlds away, the forensics team tries to reconstruct what happened there.

It was a mine and underground community populated by variant humans (not actually a separate species, just short and stocky) running semi-automated equipment to mine and be a center of industry. A third human subspecies seemed to be a ruling class of sorts, a neanderthal-like warrior caste. They traded material for food.

They suddenly started making tons of weapons.

A bunch of dragons and other big animals assaulted the place with magic powers. The warrior caste fought to the last man and to the death as the digger caste evacuated. The big battle sites correspond to 'ghostly' areas almost exactly.

A month later something too magic to conjure rained down titanic blasts of force and heat, shattering almost everything the initial battle did not.

Wow. Weird.

The Dwarf-fairy leaves and a Space Elf shows up in his place.

The ghosts are much more obvious now! Several vague, blurry outlines in the air, with a distinct sense of pride and anger and suffering and wrongness.

To the last... Our failure... Our shame... Our deaths... Unavenged...

If she tries osanwëing them does that work like it would with a subtle artist or a Maia or just not work? Hello.

It seems to work! They react at least, focusing on her and sending more half-formed impressions of despair and vengeance.

Is there anything that would help you?

Slay the dragons... Put us to rest... Nothing can make it right... Failure and loss... Remember the sacrifice...

How can you be put to rest?