L_Ender's Cataclysm: Dungeons, Bosses, and Where to Begin
L_Ender's Cataclysm is a combat mod built around difficult dungeons, challenging boss fights and the powerful gear they yield. This guide orients you before you dive into its structures.
What the mod is
Cataclysm does not add a tech tree — it adds encounters. Each of its dungeons hides a boss, and defeating that boss earns weapons and armor far beyond vanilla. Almost every structure overrides monster spawning, so finding one means finding a fight.
Early materials
A few crafting materials recur across the mod's recipes. Ancient Metal is assembled from nuggets into ingots and blocks and forms early gear like the 
Ancient Spear (four 
Ancient Metal Ingot). 
Azure Seastone is made by combining stone with 
Lacrima — eight 
Stone and one Lacrima yield eight Azure Seastone — and anchors a large decorative building set with bricks, pillars, slabs and stairs.
How to progress
Because the reward comes from bosses, progression is about preparation, not grinding recipes: build the best vanilla or modded armor you can, learn each arena, and win the fight. The boss drops then feed two systems worth their own guides — the smithing-upgraded armor lines, and the weapon fusion table that combines boss weapons into stronger hybrids.
What you are installing
283 pages, 155 items, 128 blocks and 15 structures, built on 116 crafting recipes. The item majority and the structure count together tell you the shape of the mod: it is a boss and dungeon mod, and its gear comes from fights rather than from a workbench.
The two upgrade systems
Only seventeen recipes across the mod handle gear: Weapon Fusion (8) and Smithing Transform (9). Both are identical on either version, so the endgame is stable regardless of which build your pack runs.
Amethyst Bless is a single-recipe category worth finding in a recipe viewer early, since it will not turn up by browsing the crafting list.
Processing is minimal
2 smelting and 2 blasting recipes in the entire mod. Nothing here needs an ore-processing setup — what you mine elsewhere stays relevant.
Version difference
Stonecutting is the only category that moved, from 51 recipes on 1.20.1 to 72 on 1.21.1. That is decoration rather than progression, so a guide for either version applies to the other for everything that matters.