NightWing tunnels

The NightWing Portals (aka wormholes) are used by the NightWings to make it easier to travel to other locations and to their island, since it isn't on any known Pyrrhian map. There are currently two known portals, both with one side in the Rainforest Kingdom. It is currently unknown if NightWings can create or destroy a portal, though. They give dragons a tingling feeling in their scales when they're near.

History 

It is unknown of the creator or when the portals were created, or even if they were made for a specific purpose or just so the NightWings could get out into the rest of Pyrrhia. When the Dragonets of Destiny came to the rainforest, they overheard some MudWing soldiers talking about a 'monster' that was killing or kidnapping the RainWings. A few moments later, they screamed, and Glory found them dead. After they found the RainWing village, the dragonets discovered a strange tunnel inside a rock that led to the Kingdom of Sand, coming out just a few miles from Burn's stronghold. When Glory was kidnapped by the NightWings, she was taken through another portal that took them to the Night Kingdom. 

Trivia

Jambu joked about the RainWings having their 'sun time' in the heat just outside the wormhole, which conjured up a mental image in Glory's head of a bunch of RainWings suddenly appearing out of nowhere and snoozing on the sand less than a mile away from the stronghold. (At least, he was probably joking; he might have been serious.)