Krennic has a long history with Jyn Erso's father, Galen (played by Mads Mikkelsen), a scientist who is an expert at manipulating kyber crystals — which are the key element in the making of a lightsaber blade. They were once friends, and Krennic sponsored his research and protected his family. But the Imperial weapons chief sent his Deathtrooper commandos to capture Galen when he fled to avoid working on their weapon of planetary destruction. This is the world the Ersos retreated to: Lah'mu.

"It’s meant to be a fairly secluded world," says Swartz. "We shot it in Iceland, at a place where there's beautiful black sand and green mountains poking through. The family went into hiding to a world where you wouldn’t normally have a farm, but that’s as far as they could get from Galen’s past life.”

It's named after Laamu, one of the real-life tropical locations in the Maldives where Rogue One shot scenes for the planet Scarif. The filmmakers liked it so much, they named another world after it.