This is a new mission in the Samhain 2013 event. It's a dungeon mission started from a book next to Andy in Kingsmouth Town. This mission awards you with Andy's spooky story which is one of the 10 stories needed to complete the Spooky Stories of Solomon Island mission.
WARNING! You cannot get another pumpkin once you used it. This means your first summon is your only chance. If you do not get to summon Jack, you will have to wait for another group to summon him and hope to get damage credit. You also need 5 people to place down pumpkins for this, or it's impossible to summon Jack. The pumpkins disappear after a while if not all are placed.
You can get credit for any summoned Jack if you damage him and do not die. If you die you may not get credit anymore. Once you complete the mission, you can repeat it after the cooldown and get another pumpkin.
Update: As long as you have the quest active, you can get another pumpkin if you do not have a carved pumpkin in your inventory. That means you cannot permanently lose your pumpkin anymore, but you still cannot stockpile them.
To help out Danny with his book, Andy has written a story that he remembers from his youth. Read it and find out if there is any truth to it.
Reward: 74,800 XP, Andy's spooky story, 10,000 Pax Romana, Sack of Penny Dreadfuls
After reading the story, head for the pumpkin stand in Kingsmouth Town at Coords 420/842 on the road towards the Orochi outpost.
Use U to open the vendor window with the ghost at the pumpkin stand. Buy a pumpkin, which will give you a DoT as it costs blood to buy it. Get a knife from the front of the stand and a candle from the box behind the stand. Combine all three in the crafting window to receive a carved pumpkinto the pumpkin patch in Wispwood. You need 5 people with pumpkins to summon Jack. Place one pumpkin in the middle first, then place the other 4 in the corners of the appearing circle and Stingy Jack will be summoned. This is also where Lore #8 is located.
Super JackEditIt is possible to summon Super Jack instead of Stingy Jack if the correct pumpkins are placed as seen on the ritual paper next to Andy or pinned to the tree at Jack's pumpkin patch. See this forum post for more details.
Super Jack has 12,533,426 HP and credit can be received even without being in a group as long as you damage him, similar to the Gilded Rage event.
Killing him will award you with another mission with the same name, but with different rewards. There is no cooldown on this mission. Killing Super Jack will also count towards the original mission, so you can complete both at the same time.
Reward: 299,210 XP, 20,000 Pax Romana, Sack of Penny Dreadfuls (Purple)
See Event Loot for more information about the purple Sack of Penny Dreadfuls.
Try to stand back. Hysterical Laughter seems to kill you if you are too close(?). He will periodically cast ??? which places several AoE damage areas around him, watch out for those. Grasping Vines will pull a random player close to him, try to gain distance again when you get back up. He will sometimes buff himself with Springfingered Jack which will make his burst attacks do an additional 2 hits. He also has the Pumpkin Fort buff which makes him immune to knockbacks, roots, stuns, and weakening effects.