The Heathen's Reef is a natural, arcing formation of jagged rocks forming a barrier across the entryway into the Vardưnn province by sea. The Reef acts as a funnel for ships wishing to enter Vardưnn from the north, and access to Port Sparrowclaw, Brightborough and onwards to Voldar.

There exists a causeway threading through the rocks, close to the shore under Heathen's Henge, that experienced or foolhardy pilots can navigate to shorten the passage and make direct for Port Sparrowclaw. This opening cuts the travel time of the intrepid pilot greatly, but there exists dangers. Subermeged pinnacles can tear strong hulls to ribbons, and in the narrow parts, strong cross-currents can lead the ships directly into the larger islands. During bad weather the unpredictability of the wind will deter almost any captain from sailing through the channel, lest his vessel be torn asunder.