When Blizzard first conceived of The War Within, the next World of Warcraft expansion that would literally take players inside the planet of Azeroth, there was one big worry.

“The concerns about claustrophobia were a major aspect coming into this, from the very earliest planning,” game director Ion Hazzikostas said in a recent group interview with PC Gamer.

It wasn't just the confined internal spaces developers were worried about: It was the dark. Players have historically responded poorly to zones that were unrelentingly monochromatic, dark or grim. The hellish Maw zone in the afterlife-themed Shadowlands expansion, for example, was reviled by players for ticking all three of those boxes.

So developers were determined that Azeroth's underground zones shouldn't feel that way.

“The theme of going underground can be pretty dark. So how do we navigate that sense of oppression?” asked Gabriel Gonzalez, lead visual development artist, in a group interview I attended. “What we did was really lean into a lot of story elements that could help us find ways to bring some interesting lighting, beautiful scenery, interesting atmospheric effects, that play into this fantasy of being underground–of discovering this wonderful world beneath our feet.”

The end result was zones that didn't feel like they were underground, even when they were.

“It's really not at all what you would normally expect from a cave environment,” Gonzalez said.

Take Hallowfall, for example. The zone is completely underground, but lit by a gigantic glowing crystal in the cave ceiling, so far above the floor that it's like a distant star.

“It is vast. There's a ceiling, but it's far out of your line of sight the vast majority of the time,” Hazzikostas said. “There aren't a lot of sight-blockers. It's a space that was built from the outset that if you're walking around on the ground, it doesn't feel like you're underground. You have to remind yourself.”

In the end, that should contribute to more rewarding gameplay, Gonzalez said.

“Players tend to prefer zones that feel a bit more natural, a bit more pleasant with the lighting,” he said.