How to Build and Activate an Abyss Portal
Gather the Portal Materials
An Abyss Portal is built from Abyssal Stone and lit with an Abyss Realmstone. Mine or craft Abyssal Stone, then shape it into Abyssal Stone Slab, Abyssal Stone Stairs, and Abyssal Stone Wall if you want a decorated frame. The functional frame only needs solid Abyssal Stone blocks arranged as a rectangular ring, leaving the interior empty.
Activate the Portal
Hold an Abyss Realmstone and use it on the inside of the completed frame. The portal lights and you can step through into the Abyss. Abyssal Grass, Abyssal Glass, and Abyssal Stone generate on the other side, so bring a pickaxe that can mine Abyssal Stone and a light source such as an Amethyst Lamp or Aquatic Lamp.
Return and Expand
Inside the Abyss you will find Abyssal Upgrade Kit and Abyssro among other resources. Bring back Abyssal Stone to rebuild or enlarge your return portal. If you want a matching build, craft Abyssal Stone Slab, Abyssal Stone Stairs, and Abyssal Stone Wall from the stone you collect. Keep an Abyss Realmstone in reserve so you can relight the frame if it is broken.