The experience curve is adjusted to make it faster than ever to prepare for the newest challenges, and each level along the way will provide more meaningful increases in progress and power. All expansion zones are getting more flexible, too; they'll be able* to scale to you and your friends while you level to 50, so it's easy to try a zone you've never played.
The Realm of Shadows may be the same World of Shadows as the one that becomes visible when a [Elixir of Shadows] is consumed. It may also have something to do with shadow magic and shades. Death knights, necromancers, and undead as a whole share a strong connection with the Realm of Shadows from many hints that can be seen in-game. In the death knight starting zone, death knights are given the task to enter the Realm of Shadows in order to gain their Deathcharger. Later on, death knights are eventually able to learn the ability [Raise Ally] which pulls their ally's spirit back from the Realm of the Dead and forces it back into their body. Upon doing so, a buff is applied to the player stating that: "A touch of the spirit realm still lingers..." This shows that death knights and necromancers both have a connection to the Realm of the Shadows/Dead to perform necromancy which furthers the idea that they actually are drawing their magical power from it.
During the Burning Legion's third invasion, the Knights of the Ebon Blade traveled to the Shadowlands to acquire the Aggregates of Anguish, five tormented essences of powerful souls - Admiral Proudmoore, Soulbinder Nyami, Grand Empress Shek'zeer, Grand Apothecary Putress and Archmage Arugal. Salanaar required these to conjure the Steeds of the Damned for the order's new Horsemen.
When the time comes to ally with one of these four, you’ll want to carefully consider the abilities the Covenant will provide you. Each provides two abilities tailored to the theme of the Covenant. The first of these is the Covenant’s signature ability, which is available to all Covenant members regardless of class, race, or specialization. This ability helps you explore and engage with the world in new ways, and gives you a unique tool to help solve the problems you encounter in the Shadowlands. The second of these abilities is specific to your class, and gives you a new spell or power to use in combat.
Sometimes enemies will drop Phantasma, a currency that is unique to Torghast. You may also find Phantasma from Anima Powers or breakable objects. Your Phantasma all disappears as soon as you leave Torghast. Occasionally, you may find a Broker, a Phantasma vendor within Torghast, who will allow you to spend your Phantasma to buy Anima Powers, along with other consumables that will aid you on your run.
The origins of the Shadowlands remain uncertain, but they have existed ever since mortal life first arose in the physical universe. They span all worlds, including Azeroth, on which Icecrown serves as an anchor to the Shadowlands. There are those who believe mortal souls are drawn into this dark place when they die, remaining there forever. Others hope their souls will go on to a brighter place rather than languish for eternity within the cold confines of the Shadowlands.