Censer of Eternal Agony

Censer of Eternal Agony is an item which can be purchased on the Timeless Isle. When used, it transforms the player, making them hostile to all players of either faction, and granting a Bloody Coin for each player killed while under the effects of the buff. Bloody Coins can be used to purchase various items from.

Source
Purchased for from  on the Blazing Way of Timeless Isle.

Tactics

 * Using this item essentially makes you part of a third faction. While this makes farming Bloody Coins a little easier, it also has the unfortunate effect of making you a viable target for almost every other player on the Isle. The buff's visual effect also serves to highlight you to others, essentially signposting you as an amoral assassin who will kill players of either faction for currency. Understandably, some players have therefore taken to killing such players on sight.
 * Be aware that players of your own faction will still be able to communicate with you while you have the buff. Be aware that some may be disgruntled at being killed by you, and may wish to tell you so.
 * Be aware that players you have killed will likely remain on the Isle for some time, and that the Isle is not a particularly large zone. Therefore, if you proceed to kill a number of players, be aware that you are likely creating a sizeable collection of potential enemies, and do not be surprised if they decide to repay you in kind.
 * This item's long cast time combined with its removal of 90% of the player's health makes it difficult to use for spontaneous ambush purposes.
 * Ideally, find a safe place to use this item, away from other players, guards and wandering monsters. By reducing you to 10% health, you will become an easy target, and immediately hostile to all guards and other players. Also be aware that the first time you use the item, you will earn Emissary of Ordos, which will announce your state to all players in the area.
 * Once you've used the Censer, try to restore your health as quickly as possible. Eating or self-healing are usually the fastest ways to regain health after using this item. The food objects scattered around the Isle are ideal for this purpose, and locating some of these before using the Censer will allow you to quickly regain health, minimising your period of vulnerability. Special items such as Eternal Warrior's Sigil can also be useful for this.
 * Buffed players cannot benefit from the buffs granted from Shrines. This offers non-buffed players a small advantage over their hunters. Buffed players can however still trigger the Shrines, preventing other players from benefiting from them.
 * Note that Bloody Coins are only granted for landing a killing blow - honorable kills do not award coins. You can maximise your chances of getting a Bloody Coin by removing or preventing all other sources of damage, including mobs and other attackers. When ambushing players while they are already engaging a mob, be sure to kill the mob before the player, increasing the likelihood of getting a coin. Only one Bloody Coin (if any) will be awarded per kill.
 * If no Bloody Coin is awarded (to any player), the Sacrificed to Ordos debuff will not be granted to the killed player. This allows you a second chance to kill the player (once they've resurrected) and gain a coin.
 * Because buffed players are neutral to each other, some players choose to form teams in which to ravage the Isle. Also note that the buff essentially prevents cross-faction hostility among buffed players. However, be aware that Bloody Coin drops from any kills will be awarded only to the player who lands the killing blow, and certain classes and roles such as healers will therefore be unlikely to earn their fair share.
 * Be aware that the moment your buff expires, you will return to the usual PvP rules for your faction. This means that other buffed players who were previously neutral will now be hostile, and become able (and perhaps all too willing) to attack their former ally in order to farm Bloody Coins from your corpse. Conversely, if you are being hunted by a buffed player, one possible escape is to use the item yourself - as soon as the cast completes you will become neutral to them and they will be unable to attack you. However, note the long cast time.
 * While this item makes the Celestial Guards hostile to you, it does not affect the majority of NPCs found around the Celestial Court. It is still possible to use NPCs such as vendors while under the Censer's effects.
 * Because of the hostility of the guards, players with this buff essentially have no safe place on the island. Players cannot simply remove the buff, and so must be prepared to last out its effects, or negate the buff through death or exit from the Isle.

Defence

 * For players on PvE servers, defence against this item is simple - de-flag yourself for PvP. You can toggle PvP status by typing /pvp, or by right-clicking your portrait.
 * Players on PvP servers do not have such an option, and repeated killings by buffed players can become a nuisance, particularly if playing on a busy server.
 * One solution is to group up with other non-buffed players to defend yourself against them. If you see a buffed player attacking someone, help that player to defend themselves. Buffed players do not gain any special advantage, and can usually easily be defeated by a group of opponents. Stay near other players to reduce the likelihood of being attacked.
 * Use the Censer yourself - become the hunter, rather than the hunted. Unfortunately, while this will protect you from other buffed players, it will open you up to a far larger group - the un-buffed players. Still, since un-buffed players have little actual reward from world PvP, this may be one way to avoid ganking.
 * For repeated killings, general tips for griefing apply: try playing on an alt for a while, or doing something else in-game.
 * Playing or visiting the Isle at quiet times can reduce the number of attackers, and give you a better chance of peaceful PvE action.
 * There is only one way to prevent such killings entirely - stay away from the Timeless Isle!

Achievements

 * Emissary of Ordos

Using the Censer is key to obtaining Bloody Coins, which are the subject of a series of achievements - see that page for a list.

Trivia

 * A - not to be confused with a censor or sensor - is a vessel made for burning incense.
 * The Censer originally also made players neutral to mobs - facilitating their travel around the Isle. This was changed some time during Patch 5.4.0's time on the PTR.