Kingdom of Sky features a new region to explore, located high above the skies of Norrath, known as the Overrealm. It includes a new level cap of 70 for adventurers and artisans, new items and quests, new monsters to fight, alternate ways of advancing your character (achievement points) and the ability to increase a guild to level 50.

Purchase of the expansion granted each character in any account that bought the expansion an Aviak hatchling. If the expansion was bought in a brick and mortar store, the account is granted one Carnivorous plant. The Carnivorous Plant acts as a house pet which can be fed items from the world, and depending on what is fed to it, will yield a useful item.

The Overrealm is composed of floating islands which originate from the Plane of Sky. Transportation to the Overrealm works like in The Shadows of Luclin; when a player wishes to go there, he or she obtains a teleportation shard from the overseer of a wizard spire on the ground. The overseer NPC then grants to the player character a teleportation shard which flags the player as one wanting to go to the Overrealm. Every five minutes, the spires activate, sending player characters to the Overrealm. If a player originates in Antonica or the Commonlands, he or she will be sent to the Tenebrous Tangle. If a player originates in the Thundering Steppes or Nektulos Forest, then he or she is sent to the Barren Sky. If the player originates in the Enchanted Lands or the Feerrott, he or she is sent to the Bonemire.

As with both the original game and the first expansion, a new epic quest line is included called the "Claymore" line. The start of this quest line can be completed solo in the outdoor areas, however, it will soon require a group and many segments require large investments of time "camping" the required NPCs to spawn and gain quest updates. The last parts of this quest must be completed within a raid (a group of 7+ players), the first being in an area known as "Ascent of the Awakened" in which you must have two groups (12 players). The final part takes place in Deathtoll, a zone intended for four groups (24 players), and requires an epic access quest in itself to enter. In the end players got to choose from an archetype specific reward (in some cases there are multiple choices) which at the current time was some of the (arguably) best items in the game.

Once a player has installed this expansion pack and reaches adventuring level 10, a character is granted achievement experience through discovering new areas, finding precious treasure and status items, killing monsters with specific names, completing select quests, and completing certain collections of items.