Fissure

Fissures are cracks on walls that serve as the means to traverse between Lorule and Hyrule in. They appear as a bizarre crack-shaped pattern on walls or flat surfaces. In Hyrule, they seem to release the dark smoke, while in Lorule they seem to emit light. Their icon will appear on the map when Link travels through them.

History
Fissures are first mentioned by Hilda after Link is awakened. According to Hilda, Fissures appeared due to the actions of Yuga, and now link both worlds. However, Hilda later mentions that there was a single crack in a large stone slate found within Lorule's Sacred Realm which connected both worlds even before Yuga's actions. She later states that Yuga was the one which discovered this Fissure.