Defeat Vilgax for a Vilgax Core. The Omnitrix Crafter combines it with Infinitum into a Null Void Projector. Use the projector to open a portal to the Null Void; use it again there to open a portal home. Search its rare fortress for Zs'Skayr. Floating prisons hold loot chests, and the warden's Cell Key opens the Prison Vault.
Getting there and back
Defeat Vilgax for a Vilgax Core, then combine one Core and two Infinitum in the Omnitrix Crafter to make the Null Void Projector. Use it to open a walkable portal; stepping through travels to the Null Void or returns you to your saved entry point. Projector recipe
The Projector has 16 durability and repairs with Null Crystals. Each portal opening consumes one durability. On a first arrival, the Projector points out nearby islands when it needs to create a fallback pad.
Islands and creatures
The dimension uses floating-island terrain with Null Void Stone and no fluids. Null Void Prisoners spawn there and join nearby fights. Their entity loot table lists: Prisoner Cuffs (0 to 1) Null Guardians are rare and use a tractor beam; Lepidopterran scouts spawn in small groups and spit slowing slime.
Prison blocks and Plumber wrecks
Floating prison blocks appear about once per 250 chunks. Cell spawners hold prisoners, and a persistent Prison Warden guards a keyed vault. Wrecked Plumber outposts appear about once per 300 chunks with badges, a blaster, suit pieces and Taydenite.
Crystals and the fortress
Null Crystal Ore and rarer Taydenite Ore generate in Null Void Stone. Null Crystals repair the Projector, while Taydenite is used for Plumber gear and the glider. The fortress placement filter is 1 in 400 chunks. The fortress contains loot chests and a persistent Zs'Skayr encounter.
Zs'Skayr drops Master Control. Use it while the Omnitrix is equipped to unlock every alien and remove timeout and recharge.