The Null Realm is a location not on the map, it can only be reached after defeating or capturing Whis on Birth Island. After your battle with Whis, the Daishinkan will appear and invite you in. If you decline, the cube of the gods will be on Birth Island, and interacting with it will teleport you to the Null Realm
After entering the Null Realm you will be in an arena with Jiren, and the Daishinkan and Zeno waiting on the top. HIGHLY RECOMMENDED THAT YOU SAVE BEFORE TALKING TO DAISHINKAN(the battles that follow do not allow for healing etc, and you only get ONE try on these).
All fights in the Null Realm are lvl 70+ so bring your strongest fighters, and A LOT of ultra capsules(if you saved your golden capsule this might be where to use it).
(You can save after this battle)
After this battle, Zeno summons Super Shenron and he grants you one wish(golden capsule, god stone or 2 potara). After choosing your reward, you will battle Super Shenron
- Super Shenron (lvl70)
Zeno then asks if you want to fight him(you CAN SAY NO HERE AND SAVE)
- Zeno (lvl 80)
After either defeating or capturing Zeno the Null Realm is empty