Ruler of Thul

If Polar Explorers or Ruler of Thul are in play and an oversized unit on the top row moves 'up' one row to wrap around to the bottom, what happens?

This ability only allows movement across the borders, not ongoing occupation. Units cannot balance on the edge of the realm and an oversized unit that finds its way there falls to one side or the other. Its controller places it in the closest legal position, controller's choice if tied.