Phasing Phasing is a technique commonly used in MMORPG s . This refers to the technique of having a certain area look different to different characters . When something is " phased " it means it exists in the same virtual geography as other creatures or objects , but is not visible and can not be fully interacted with . How it Works . Data on the location of game objects , players , and NPCs is not stored in the " World of Warcraft " client and must be sent from the server . Phasing , in a sense , decides not to send certain data based on criteria . As an example , you may have a quest to get the head of a named NPC . After turning in the quest , the server records that it should not send data about that NPC to you . The next time you go there , even if the NPC is still there , you will not be able to see it . By using combinations of phasing , entire areas can change from grasslands to a city by use of game object phasing and NPC phasing . Appearance . NPC phasing . NPC phasing is recognized by an NPC which should be at a location , but is completely gone when viewed by someone else . Player phasing . Player phasing is recognized by not being able to see a player . Early uses of this was death , stealth and invisibility effects which caused the server to only show hidden players to certain people ( i . e . when you are in spirit form you can only see other " spirit people " — other players " also " in spirit form . ) Object phasing . Game object phasing is the easiest to recognize and usually requires multiple phasing techniques . Game objects can be anything from a chair or chest , to a building . In most cases , players that can interact with phased buildings must also be phased , otherwise it would appear that players were walking in the air . Types of Phases . In Wrath , phasing is implemented in three different , and quite distinct , ways . The first is the phased instance . The only example currently is the Death Knight starting area . Beginning Death Knights are not actually in a phased section of the Eastern Plaguelands , they are actually in a large instance modeled after the eastern portion of the zone , similar to the way Old Hillsbrad is an instance modeled after a portion of Hillsbrad Foothills . This is indicated by the fact that the starter area is surrounded by invisible walls that prevent players from leaving , as well as the fact that players have a different General and Local Defense chat channel . Second , there are temporary phases , like Fleshwerks in Icecrown . Once you complete the quests that the area is phased for , it returns to normal . There are a few other examples , such as the phase you enter in Zul ' Drak when riding Gymer . There is also the Court of Bones in Icecrown , which only phases if you have certain quests from the Argent Tournament . Finally , there are permanent phases , where you are unlocking an area , such as Shadow Vault and Dun Niffelem . Often , these areas are changed through a series of phases , and once the quest chain unlocking the area has been completed , the character will always see the area in its new state . A form of the permanent phase , terrain phasing , makes an introduction with Cataclysm . This phasing involves changing the land around you , which happens like other phases , through quests and events . Usage before Wrath of the Lich King . Before Wrath of the Lich King , phasing was used in stealth and invisibility mechanics . Events such as the opening of Ahn ' Qiraj and the taking over of the Isle of Quel ' Danas were simply different realm databases adding game objects and NPCs for all players . Phasing was invented as a bug fix for the Shattered Sun Offensive daily quests in Blade ' s Edge Mountains : † and . In Wrath of the Lich King . In " World of Warcraft : Wrath of the Lich King " , Blizzard has made full use of this system . The most well - known examples are , which looks different to the character depending on his progress through the DK questline , and the Angrathar the Wrathgate line of quests , which end with for Alliance characters and for Horde characters . To characters having completed the questline , Alexstrasza is located in front of the Wrathgate and Varimathras , who was killed along with Grand Apothecary Putress , will no longer be in Undercity . For players on certain steps of the quest , the Undercity will also be inhabited by demons . Another example is the existence of Alliance NPCs in front of the Undercity which are not visible to players in a different phase of the quest . Phasing is also used in ( not by far a complete list ) : In Cataclysm . Phasing will play a huge role in " " , and not just in the newly made zones , but a good amount of the revamped zones as well . A few of the known phase changes are that of the starting areas for the newly announced races of goblins and worgen , in much of the same way the death knight starting zone was handled . . . except with the new terrain phasing feature . Limitations . Currently , phasing is unable to change the base terrain of the world . This means that the normal ground must not change in texture or positioning . An example would be the Court of Bones at the Wrathgate having burnt ground prior to being burned by the Red Dragonflight . Cataclysm unlimited . This however with the " World of Warcraft : Cataclysm " changes those limits . Terrain will be able to phase like never before , land will sink beneath the waves as well as rise above them . A raging fire will be able to expand further along as time moves forward . Whole mountains could crumble and fall leading way to new lands . With this technology you could see , for example , a harbor built before your eyes , without the use of in - game patches . Garrison s and the Mists of Pandaria farm are also using this a lot .