Vent

A Vent is a pathway that Heartless use to travel to different worlds from the Realm of Darkness, invading the worlds. The Vents were created out of negative thoughts and emotions, from people with darkness in their hearts. They must be sealed by the Keyblade in order for the Vents to close, causing no pathway for Heartless to get to a world, which also strengthens a world's barriers.

They are also shown in dreams of wielders of the Keyblade, of different locations they may be at, as shown when Kairi dreamt of Destiny Island's Vent. The stronger the light in a person's heart, the stronger the image is. Vents are viewed similar to Keyholes, except they are shaped like flowers.