The Sith cave on Mustafar, following the construction of Sith Lord Darth Vader's Fortress had a portal. The portal used the fortress to amplify it's power. Sith Lord Momin claimed the portal could bring Vader's deceased wife, Padmé Amidala, back to life. Vader attempted to open the portal but was unable to do so due an attack by the Mustafarians. This allowed Momin to resurrect himself.
After Vader defeated Momin, Vader was able to open the portal. As he entered the portal, Vader's soul left his body. Inside, Vader saw visions of his mother, Lord Sidious, and his younger self. Vader then saw his memories of past events in his life from his victory in the Boonta Eve Classic to a duel with his former apprentice. Vader came across vision of the Jedi Temple, where he was confronted by apparitions of his fellow Jedi, his former master and Darth Sidious. After defeating the apparitions, Vader found his wife. He asked Padmé to come with him, but she said that his Vader's former self, Anakin Skywalker, was dead to her. Amidala took her life and Vader returned to his body. In his anger, Vader destroyed the portal.
The Jedi Temple on Lothal had a portal that led to the world between worlds, containing countless other portals that could be accessed across the space-time continuum. Ezra Bridger heard voices emanating from many of them, and witnessed the duel on Malachor between Tano and Vader through one of these portals.
Bridger soon found that he could interact with them and in doing so, was able to save Ahsoka by pulling her through the portal into the world between worlds. Due to Ezra's interference, the veil between dimensions was weakened and Palpatine was also able to peer into it with the help of Sith magic. However, he could not physically enter and needed Ezra to fully access the power the dimension held. After having fought off Sidious's attempts to capture them, both Ezra and Ahsoka returned back through the portals they had come from, with Ahsoka returning to Malachor and Ezra back to Lothal.
- Darth Vader: Dark Lord of the Sith 23: Fortress Vader, Part V
- Darth Vader: Dark Lord of the Sith 24: Fortress Vader, Part VI
- Darth Vader: Dark Lord of the Sith 25: Fortress Vader, Part VII
- Star Wars Rebels – "Wolves and a Door" (First appearance)
- Star Wars Rebels – "A World Between Worlds"
- Star Wars Rebels – "Family Reunion – and Farewell"
- A Crash of Fate (Mentioned only)