The service will launch with patch 4.0.1 and lets you modify the stats on items.

Just in time for the launch of patch 4.0.1, Blizzard has released a preview of the reforging system that is going live today following the extended maintenance. NPCs in all major cities will let players modify an item's stat values, which means gear is now customizable.

Stamina, Intellect, Strength and Agility cannot be altered via reforging. However, the following secondary stats can be changed: Spirit, Hit Rating, Expertise Rating, Critical Strike Rating, Haste Rating, Mastery Rating, Parry Rating, and Dodge Rating. Basically, you can take any secondary stat that's already on the item and allocate roughly 40% of it toward another secondary stat of your choice.

The service costs gold and only works on gear that is item level 200 or higher. You can read an example of how the system works in the full preview after the jump.

Cataclysm Preview: Reforging

Originally a magic brought to the citizens of Azeroth by the Highborne, reforging will provide a new means for players to customize their gear in World of Warcraft: Cataclysm. NPCs offering reforging services will be located in all major cities, ready to assist in customizing items by altering the stats they provide. Players can use reforging to modify an item's stat values, or to undo any previous changes and allow different customization choices.

What Makes a Stat

All performance-boosting stats present on items fall into two categories: primary and secondary. In Cataclysm, the primary stats are Stamina, Intellect, Strength, and Agility. These stats are considered set in stone and cannot be altered via reforging. However, most secondary stats can be altered. Secondary stats that can be altered through reforging are Spirit, Hit Rating, Expertise Rating, Critical Strike Rating, Haste Rating, Mastery Rating, Parry Rating, and Dodge Rating. Any of these secondary stats can be adjusted and added via reforging NPCs.

Reforging Items

The act of reforging is quite simple and will allow players to customize gear to their liking. In order to take advantage of this feature, a player needs to speak to a reforging NPC in any major city and provide them with an item to be reforged. Items to be reforged must be level 200 or higher; you can find an item's level by turning on the feature under the Display section of the Interface Options. After choosing an item to be reforged, the player can choose any secondary stat already present on the piece and allocate roughly 40% of it toward another secondary stat of their choice. The cost for reforging is the vendor price of the item. Some restrictions apply -- you can only reforge one secondary stat on an item at a time, and you can't bolster a secondary stat that's already present on an item. You can, however, undo the allocation and pay to reforge the item again. This is especially helpful in keeping stats relevant to your character as you acquire new items and skills, and change talent builds.

Putting It Into Practice

Let's say you want to reforge Apocalypse's Advance (ilevel 271). You like the Critical Strike Rating on the item, but you don't need the extra 70 Hit Rating it provides. You can visit a reforging NPC in any major city, place the item in the reforging window, and choose to reduce the Hit Rating in order to add another secondary stat for a little under 14 gold (the vendor price of the item). You can choose from any stat except Critical Strike Rating, since that's already present on the boots. So, maybe you want to increase your Mastery Rating. When you choose that stat from the dropdown and confirm your purchase, the item's Hit Rating will be reduced to 42, and 28 Mastery Rating will be added. If at any time you change your mind or want to alter the reforged stat, you can undo this decision at the reforging NPC, restoring the item to its original stat values. An item's primary stats will always dictate what classes and builds an item is meant for, but with reforging you can nudge the secondary stats to help make them a better fit for your character's needs. Reforging is yet another option for customizing your gear. The choice is yours!