Where iron?
The depths of these underground caverns, took no time whatsoever to unravel its collective heat. The team started feeling it right away, and broke a sweat too.
As for those three albino women, they were used to such procedures. Apart from that, their bodies were specifically designed to endure both heat and cold. Their tolerance could be based on evolution, adaptation, a genetic mutation, or even pure luck, but the odds and ends didn't matter nonetheless.
They were useful today, and proved to be excellent guides. If Gustav had somehow made it here alone, he'd easily get lost in these maze-like caves and tunnels, which would later on overheat him to the point of death.
He wasn't as spacially aware in comparison to these albino ladies. They were over-qualified, and lived down here for a reason.