Uncle Pom is an elderly coal miner dwelling deep beneath the mining town of Slag Ravine. He possesses a stocky build, wild white hair, and a bushy mustache and beard. His typical attire includes a cap and a worn, patched coat, while his knapsack holds supplies for life underground: a bedroll, canteen, and lantern.

He spends most days within the deeper, abandoned sections of the mines, rarely surfacing. The townspeople call him "Uncle Pom" with affection, recognizing his role as their lookout and guardian, especially fond of the young miner Pazu. His knowledge of the subterranean world runs deep; he claims the rocks themselves "speak" to him.

When Pazu and Sheeta flee into the mines, Pom encounters them. He demonstrates how rocks glow faintly in the dark due to traces of Aetherium, also known as Levistone or Volucite, explaining the technology to mine it vanished long ago. Seeing Sheeta's crystal necklace glow like the rocks, Pom identifies it as pure Aetherium. He states only the ancient Laputans could craft such crystals, confirming the legendary floating city's existence. However, he finds the crystal's "voice" overwhelmingly loud and sad, urging Sheeta to hide it again.

Pom shares a warning about the crystal's power: while capable of great things, it fundamentally belongs to the earth. He suggests forgetting this connection leads to misery, hinting at Laputa's downfall stemming from its people's detachment from the land. After offering shelter and guidance, he leads the children safely out of the mines and bids them farewell. His understanding of Laputa's legends and Aetherium's nature connects the protagonists' journey to the film's mythological elements.