Lind had studied the changes in his body since becoming a Sky Realm. While his need for food and water decreased immensely compared to the World Realm that still had to indulge every 3 to 4 weeks, the need for air did not change.
Less air was more than acceptable as the body was much more efficient, but if the air was removed forcibly, the cultivator still died. Worse, they did not even understand what was happening as they were looking for attacks or defending against formations.
By creating vacuums, the air in each cultivator was forcibly expelled. The blood vessels in the brain and body burst all at once and death is instantaneous. It was very vicious but he had few options without knowing what he was facing.
