Hanging off the face of a cliff, an ice axe the only thing between him and death, a Sherpa climber named Chhiring Dorje swung to the left. A massive ice boulder ripped off above, hurtling toward him.

It was the size of a refrigerator.

The underbelly caught, and the mass flipped, cartwheeling down. It tore past, skimming Chhiring’s shoulder, then vanished.

Brooof. It slammed into something below, shattering.

The mountain shook with the impact. Powder shot up in a column.

It was near midnight on August 1, 2008. Chhiring had only a hazy idea of where he was: on or near the Bottleneck of K2, the deadliest stretch of the most dangerous mountain.