Different from the similar looking Pumpkin Chests, Pumpkin Treasures are animated reward chests that cannot be crafted, but instead could only be traded from the Pumpkirus when these NPC traders appeared during the Halloween event 2017 Pumpkiru's Candy Campaign that started on October 18th 2017 and ended on November 15th 2017.
These valuable treasure chests contain(ed) Halloween-themed blocks and objects from 2016 and 2017, including rare non-craftable Potions, and even always one random Halloween-themed rare crafting Recipe too.
How to obtain
You can alternatively obtain these rare animated chests if another player gives (any of) them to you since they are tradable. They cannot be bought as part of building kits for Blueprints though, because these chests cannot be captured with any Capture Blocks.
To receive the content of the chests that you have obtained from Pumpkirus (or from other players or from an unlocked reward bundle from the Pumpkiru's Community Candy Campaign), you only have to place the reward chests from your quickbar into the game world.
Different from storage containers, these chests will then automatically open after displaying a special animation. Nearby yellow Pigsies, red Rocksters, green-blue Chizzards and any type of peaceful surface Leafi will be attracted to the chest while it opens.
You can right-click on these chests or activate them (by typing "f" as the default key) while pointing your cursor at them even without waiting for the animation to finish though if you should be in a hurry.
The Great Pumpkirus and (way more rarely) sometimes Pumpkiru Jr.s will usually appear for ca. one month around Halloween here and there on the surface of Creativerse game worlds within a certain proximity around player characters; but only at night, starting around ingame time 10:37 - 10:47 PM.
More Pumpkirus will spawn as soon as players enter new areas (only on solid blocks, not in liquids), so it is recommended to run or fly over the landscape and talk to every Pumpkiru that will spawn during Halloween event-times to then select the ones that offer the more expensive Pumpkin treasure chests. The orange Pumpkiru symbol on the compass should be of great help to locate Pumpkirus.
When activated (like any Pet or activatable object in the game world), a dialogue window pops up that allows players to trade with the Pumpkiru.
During the Halloween event 2017 (Pumpkiru's Candy Campaign) that started on October 18th 2017 and ended on November 15th 2017, each Pumpkiru had a fixed initial offer of one of the three types of Pumpkiru reward chests - either a Pumpkin Treasure (for 20 Pumpkiru Candy), or a Royal Pumpkin Treasure (for 50 Pumpkiru Candy) or else a Pumpkiru's King Treasure (for 100 Pumpkiru Candy).
It was recommended to save 100 Pumpkiru Candy or more and then to search for one of the Pumpkirus that would offer the most expensive chest for 100 candy, until you had collected all the Halloween-themed Recipes at least once.
The items found in cheaper chests were usually only common ones, while the more rare items (and even the non-craftable Bat Juice) could more often be found in the more expensive Pumpkin reward chests, especially in Pumpkiru's King Treasure chests.
Talking more often to the same Pumpkiru would not change its initial chest offer, only his additional monologue often changed by that. After trading one or more chest/s, a Pumpkiru often randomly offered another type of chest. Buying cheaper chests would not "unlock" Pumpkiru's offer of more valuable chests though in 2017.
Pumpkin Treasure chests (that could be bought with 20 Pumpkiru Candy from the Pumpkirus in 2017) mainly contain already crafted Haunted Nights blocks and objects that were already introduced in 2016, often together with some of the newer bombs (Scare Flares and/or Flaming Skulls), Haunted Fireworks and/or (more rarely) Marigold Potions, but never any Halloween-themed crafting Recipes and usually also no Bat Juice.