Pathfinder U2

When the dragon was severely injured, it left Rimeskull. The seven pillars surrounding the central pillar are each marked with hundreds of Thassilonian runes—arcane formulae describing the basic tenets of one of the seven Thassilonian schools of magic. The seven pillars form the points of a huge Sihedron, and the heroes noticed a small keyhole hidden four feet off the ground on each pillar, facing the central monolith.

The white dragon became invisible right before it entered combat.   It flew low under the heroes (just above the standing stones) and used its breath weapon, at the same time relying on its frightful presence to weaken their morale. When the heroes scattered, he singled Gryxxa out in between rounds when it breathed and made a flyby tail slap followed by a bite so that it snatched her, carried her aloft, and breathed on her. The heroes are still fighting this battle.