NightWing tunnels
The Portals, also referred to as the tunnels, were created by Stonemover and were used by the NightWings to make traveling to their island and to other locations easier. There are currently two known portals, both with one side in the Rainforest Kingdom. One leads to the NightWing's destroyed island, and the other leads to the Kingdom of Sand. There may be more, but they have not been sighted.
The portals seem to give dragons a tingling feeling in their scales when they are near, described as an "awkward wrongness" and that the portals gave off the "I should not be here" feeling, possibly a result of animus magic.
History
The portals were created approximately two years before the dragonets hatched, by Stonemover. When the dragonets of destiny found the RainWing village, they discovered a strange tunnel inside a rock that led to a location just miles away from Burn's Stronghold.
When the NightWings captured Glory and fourteen other RainWings, she was taken through another portal leading to the Night Kingdom. She eventually escaped the NightWings using the portal. Later, she lead her army through this portal to the Night Kingdom.
The NightWing tunnel that leads to the rainforest was destroyed by the eruption of the NightWing volcano, but the one that leads to the Kingdom of Sand is still intact.