Here is a guide for the new GW2 explorer achievements introduced with the Halloween Patch. This is a work in progress and will be updated as more as discovered. A lot of these achievement locations are swarming with mobs with some are mini dungeons or mini-dungeon/jumping puzzle hybrids. Bringing a friend is highly recommended for this achievement hunting to avoid frustration!
Vexa’s Lab is a new jumping puzzle/mini dungeon in Fireheart Rise introduced with Halloween patch. Here is a comprehensive guide for the new puzzle/dungeon. The new puzzle/mini dungeon hybrid can be done with two players but might be a tad bit rough if you are doing it solo.