Every sci-fi or fantasy setting needs at least one precursor civilization.
Here's some tables to generate one.
Technological Level: (1d6)
1- Mohenjo-Daro - metalworking, basic plumbing, irrigation
2- Han Dynasty / Ancient Rome - concrete, ironworking, waterwheel power
3- Song Dynasty - gunpowder, printing press
4- Industrial Era - motorized transportation, mass production
5- Digital - electronic communications, computers
6- Futuristic - sapient AI, interstellar travel, terraforming
1-2 - The ancestors of an extant culture. Their descendants might be proud of their heritage, or entirely
unaware of it.
3 - An extinct humanoid species. (Remove one race from the "playable" list.)
4 - An extinct non-humanoid species.
2- Environmental catastrophe (natural) - volcanic eruption, natural climate shifts
3- Environmental catastrophe (artificial) - pollution, soil depletion
4- Plague (including famine caused by crops/livestock dying off)
5- Magical disaster - wizards' war, divine wrath
6- Construct uprising (futuristic tech level/high magic setting only)
7- A natural resource (usable metal, fuel) running out
8- A combination of factors - roll twice and combine