Fallen Lore-um
Fallen Lore-um is a secret advancement that takes place within The Fallen Forum Dungeon and miscellaneous locations around the King's Valley and Celsian Isles.
Intro
Before starting this advancement, you'll need an instance of The Fallen Forum. At minimum, the advancement can be done in 2 weeks worth of Forum runs, but can take more if you don't get the branches needed. If you do the steps in this guide while in race mode, you can abandon your instance and complete the advancement without having to spend multiple weeks doing so.
The steps below are listed in order of branches, so skip to the section that corresponds to the branches rolled in your forum.
The Conservatory
Step 1:
Head to the Growth Labs. In the desert-themed area, there's an ahnk symbol above the staircase at [-1278, 151, 8532]. There is a hidden wall in the lower few blocks of the ahnk. Walk through this wall to obtain the Arm of an Ent.
Step 2:
Bring the Arm of an Ent to the library in Lowtide. You'll need to press a series of buttons located within the archives to open a secret room in the teleport hub. A YouTube link to a detailed guide for this step can be found below.
After placing the Arm of an Ent in the item frame, it will be upgraded to an Ent Seedling.
YouTube guide: https://youtu.be/WOQ4yrlZzpo?t=194
Step 3:
Take the Ent Seedling to The Conservatory branch. Take the first right and head down the path to the Asian-themed house. Flip the trapdoors at [-1200, 35, 8269] covered up by leaves and there's a room with an item frame behind. After placing an Ent Seedling in the item frame, it will be upgraded into a Wooden Needle
Conscriptorium
Step 1:
Grab the Bottled Spirit from a chest in the starting room, behind a hidden wall on a bookshelf on the right side of the room at [-1237, 171, 8462]. The potion duration of 2:31 leads to the next step.
Step 2:
Head to the Apartments in Sierhaven. Go down to the basement, and enter the code 231 into the keypad at [-2156, 139, 774]. Like in the quest A Little Spark, after entering the code you'll be teleported to apartment 231. In this apartment, place the Bottled Spirit in the item frame. After doing so the Bottled Spirit will be upgraded to a Shade Telemetry.
Step 3:
Head back into The Fallen Forum. Here, you'll want to enter the Conscriptorium Branch. High up on the South wall of the main area you can find a door located at [?]. After entering the room, you'll find an item frame. Place the Shade Telemetry in it and it will be upgraded into a Shadowed Vial.
Living Quarters
Step 1:
You can find the first item for this step within the large pit. Near Chainbreaker #2, at [-1138, 132, 8444], there's a gravel in the wall. Mining this will reveal test tubes, the same ones used in The Olive Branch's puzzle. Walk through the test tube with no concrete powder in it, and inside a chest has the Letter to a Loved One.
Step 2:
Head to Frostgate for the next step. In the undercity, where small apartment-like rooms are, there's an NPC by the name of Diana. Walk through the painting in their room at [-1505, 81 990] to reveal a secret passage. At the end of this passage is another NPC, who will trade your Letter to a Loved One for an Alleria's Locket.
Step 3:
Make your way back to the Forum and head to the Living Quarters branch. Below a bridge above water there's a door covered up by leaves at [-1190, 85, 8534]. After opening the door you'll come across an item frame, and when placing the Alleria's Locket inside it will be upgraded to a Damaged Chassis.
The Final Step
After obtaining and upgrading all 3 items for the advancement, you'll need to defeat the Forum boss itself, False Spirit. In the room after the cutscene with Teal, climb up the tree stump and flip the trapdoor at [?]. A chute will be revealed to which you'll want to fall down. In the basement of the chute, there are 3 smithing tables, each with their own item frame on them. Place all 3 upgraded items on the smithing tables and you'll be rewarded with the Fallen Lore-um advancement and the Replica Olive Wool.