The Etherium Mine is a location from the 1985 animated series She-Ra: Princess of Power.
She-Ra: Princess of Power
The Etherium Mine was a prosperous source of material for the city of Dryl for many years. The city grew in cize and many large metal structures were built compared to the usual small villages seen on the planet.
However, the Evil Horde came to make use of the Etherium Mine as they used Etherium to power their machines. They forced all the inhabitants of Dryl to work the mine and left a giant Robot Guard behind to make sure they did their job. When the Etherium ran out, the Robot grew angry and drove the villagers back into the mine. It would have kept it in there forever had She-Ra not arrived on Swift Wind and destroy the Robot.
The men and women of Dryl wanted to join the Great Rebellion and never be slaves again, but Hordak wanted to make an example of Dryl, to discourage other towns of rebelling and so an entire Horde army attacked and destroyed the city. Once Dryl had been evacuated and all the villagers had taken refugee in the mine once more, Hordak ordered his troopers to burn the city to the ground.
With the rest of the Rebellion held up at Castle Bright Moon, She-Ra and Swift Wind needed help. The Sorceress of Castle Grayskull heard her call and sent Prince Adam to Etheria, where he arrived in the middle of the Horde Assault on the city. Soon, Adam was replaced by He-Man and together with his sister he assisted the villagers against the Horde. However, He-Man was surprised to learn that She-Ra was unable to save the city from being burned to the ground, for the Horde ruled planet Etheria. The villagers, adament to join the Rebbellion and led by Collon, knew they could always built new homes for themselves and trade in all their posessions for someting they did not have before: their freedom.
So, She-Ra went to warn the rest of the Rebels while He-Man stayed behind in the mine. Hordak ordered his troops to fire all their Freeze Rays, as well as the one on his own Horde Crawler simultaniously at He-Man, managing to stun even the mightiest man in the universe and blocking the only entry into the mine with rocks.
He-Man was too weakened to make a new way out of the mines in time, so Collon encouraged his fellow villagers to make away out themselves uring their mining equipment. Whith a little help from She-Ra, who had returned, they managed to break through to the other side and He-Man was saved at the last moment from the collapsing mine by his sister. The villagers of Dryl finally found themselves in a save haven, Whispering Woods, where their new lives as members of the Great Rebellion could being.