Thresan: Skyflag

From BoardGameGeek:

Thresan: Skyflag is a two-player abstract strategy game played across three stacked 6x6 boards (Terran, Meridian, Empyrean) connected by a central Nexus column. Each player commands five pieces: a Captain, two Soldiers, a Rover, and a Pilot. Soldiers promote to Captains by reaching the far rank; Rovers and Pilots are the game's transports, capable of lifting pieces between boards through the Nexus. The objective is to capture the opponent's flag, which begins on the Terran board. Lifts add a vertical dimension to a chess-like capture game: pieces can be moved up or down the stack to attack, defend, or escape. With 108 squares across three planes, Skyflag explores a wider tactical and strategic space than a single 8x8 board while keeping the piece set compact. Skyflag is an edition of the larger Thresan game system; the underlying game traces its lineage to Ashtapada, the ancient Indian 8x8 game that also gave rise to chess. -description from the publisher