Nether

The Nether is a dimension that may be added to Minecraft Pocket Edition in a Future Update It can be accessed by a portal consisting of Obsidian in a rectangular shape that needs to be ignited using Flint and Steel, though the existing Nether Reactor may be still be used.

Landscape
The Nether is a hell-like dimension, consisting of low light level, lava oceans, and most landform consisting of Netherrack. It also contains Fortresses made out of Nether Bricks. It also has random veins of Nether Quartz Ore.

Mobs
Zombie Pigmen spawn in large numbers in the Nether. It is unknown which other mobs will be added to The Nether in Minecraft PE, but in other versions they are:
 * Ghasts
 * Blaze
 * Magma Cubes
 * Wither Skeletons

Trivia

 * The Nether Reactor may still be used instead of the Portal.
 * Tomasso of the Pocket Edition Team has tweeted that the Nether is on 'his to-do list' and may soon be added.
 * The Nether has been replaced by the Nether Reactor in PE.