Okay so this is what I did to get all the current possible Blood and Madness living story achievements in under three hours.
Upon logging into Guild Wars 2 for the first time after the latest patch, you will receive a mail detailing the current living story. Waypoint to the Haunted Nolani Waypoint in the Black Citadel, talk to the living story representative and enter the story instance (it is advisable to bring condition removing skills for this instance). Follow the star marker until you reach Tassi (you can go around the second gate which is locked by using the hidden corridor on the side). When Bloody Prince Thorn appears, distract him by just autoattacking and surviving his conditions. When Tassi tells you to throw everything at Thorn, pick up the random items on the ground and throw them at Thorn until the candy corn spawns at the perimeter of the room. Keep throwing candy corn at Thorn until he retreats. This completes Containment.
When you exit the instance, you will receive another mail from Tassi with 20 limited Halloween finishers. Use all of them and enter the Heart of the Mists (PvP). Equip whichever Halloween finisher you got in the mail and head north to the sparring NPCs area. Attack any profession sparring NPC (preferably one that your profession has no problems beating) until the NPc goes into downed state. Use a finishing move but cancel it before the animation completes. As long as the finishing animation starts, it counts toward the achievement. Repeat this 20 times and you will complete A Stomping Good Time.
Next, head to Queensdale, Kessex Hills or Gendarran Fields and find a Mad King Door or Bloody Prince Door. These doors disappear within 10 seconds to one minute of spawning so it is easier to camp a door’s spawn point since they respawn every one to three minutes. Upon activating a door, one of these things will randomly occur.
- some Halloween foes spawn and the door disappears.
- one to five Trick or Treat bags will spawn and are lootable, and the door disappears (low chance).
- a door event starts (low chance).
- the door opens and grants access to the Mad Labyrinth for one to three minutes (high chance).
You’ll want the fourth possibility to occur, so enter the Mad Labyrinth when that happens. Mad King Doors and Bloody Prince Doors in the Mad Labyrinth will always start door events when triggered. Now, just follow the zerg around completing door events and killing Halloween foes which all drop Trick or Treat bags. While following the zerg around, you will most likely encounter the Labyrinth Horror (spawns randomly anywhere in the Mad Labyrinth), Grand High Viscount of Candy Corn (door event in northwest corner) and the Skeletal Lich (door event in southeast corner). All these bosses are legendary ranked. Also, the trash foes in the Mad Labyrinth hit much harder than in the outer world. It is highly recommended to bring high armor, high health characters with plenty of condition removal (read: NO FULL BERSERKERS) to survive the Mad Labyrinth.
Killing all three legendary bosses will get you Bonebreaker, Candy Corn Crusher and Death to the Undying. Completing 50 door events will get you Shut the Doors. After completing 50 door events, you should have more than 50 Trick or Treat bags so open them all for Something Good to Eat. If you are short of 50 bags, buy some from the trading post.
Completing all of these achievements and the four daily living story achievements so far should put you at 11 out of 13 achievements for the meta reward. The last achievement, A Royal tradition, will only be obtainable on 30 October.