Deeper and Darker adds a new dimension to Minecraft called ‘The Otherside.’ The only way to reach it is by igniting a Portal, which can be found within the relatively new Ancient Cities.
How to Light a Portal
If you haven’t already, you will need to find a large portal frame, which will allow you to reach the Otherside. These can be found spawning within Ancient Cities, and you must build your way up to them.
Ancient Cities spawn within the Deep Dark, so travel deep below the surface. If you are unable to find an Ancient City, then you can enter the following command, provided you have cheats enabled: /locate structure minecraft:ancient_city
Now, the only way to light the portal that leads to The Otherside is by having a Heart of the Deep. This is a new item provided by Deeper and Darker, and can only be obtained by killing the Warden. Sadly, it isn’t an easy fight, as the Warden has 500 health.
To summon the Warden, make a lot of noise inside an Ancient City. When Sculk Shriekers activate four times, a Warden will appear from the ground. An easy way to beat the Warden is by gaining high ground, and fighting it with a Bow and Arrow, as it won’t be able to climb towards you.
Wardens use vibrations to locate you. Although occasionally, they can sniff around, allowing them to find you even without vibrations. If you can beat the Warden, they will drop two new items: Warden Carapace, and the Heart of the Deep.
Right-clicking a portal frame within Ancient Cities while holding a Heart of the Deep will create a portal to The Otherside. Sometimes, this won’t work if the portal frame is covered in Sculk Veins, and these need to be cleared. Your Heart of the Deep will be consumed once the portal is ignited.
The Otherside is a hostile dimension. Therefore, it’s recommended that you don’t enter the portal immediately. You may be attacked as soon as you enter the portal. Instead, ensure enough equipment to survive, as well as building blocks and food.
Players within The Otherside will also be hit with the ‘darkness’ debuff if they are in the Otherside without a Warden Helmet equipped. If you enter the Otherside, a Portal exists to allow you to return to the Overworld anytime.