Fissure

Fissures are cracks on walls that serve as the means to access to Lorule in. Here, they appear as a bizarre crack-shaped pattern on the wall; in Hyrule they seem to release the dark smoke, while in Lorule they seem to release the 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 they are now linking both worlds. However, Hilda mentions later in the game that there was a single crack in a huge stone tablet in Lorule's Sacred Realm which connected both worlds even before Yuga's actions, as he was the one which discovered this fissure.