The Soul Great Sword drops from the Possessed Paladin, the boss waiting behind the 
Somber Trapdoor at the bottom of a Collapsed Kingdom. It drops every time the boss dies, so the hard part is getting down there.
It swings for 14.5 attack damage at a speed of 1.3, which is slower than a 
Netherite Sword but hits for close to twice as much. It reaches about a block further than a normal sword and never takes durability damage. It also has two right-click abilities, and which one you get depends on whether you’re sneaking.
Obtaining
There’s no recipe for the Soul Great Sword and it isn’t in any 
Chest loot table, so you have to kill the Possessed Paladin for it. That means working down through a Collapsed Kingdom and crafting two 
Somber Keys on the way, a long trip more than a hard one.
Find a Collapsed Kingdom
Underground, four vanilla biomes
The structure generates underground in Plains, Forest, Birch Forest and Old Growth Birch Forest, and kingdoms sit about 110 chunks apart. Most of it is buried, but a tall gatehouse sits on the surface, so once you’re in the right area it’s easy to spot.
With cheats on, the locate command takes you straight to the nearest kingdom and tells you how far away it is. On a server or a survival world without cheats, the Eye below does the same job for the cost of a few Soul Torches.
Without cheats, an 
Eye Of Ghost will find the kingdom for you, which is 4 
Soul Torches around an 
Ender Pearl, thrown and followed like an 
Eye of Ender. It only searches the four biomes above, so throw it from somewhere green, and bring a spare, as it usually drops back down but sometimes shatters.
Once you’re there, go in through the gatehouse rather than digging. The rooms below are walled in Indestructible Block that no pickaxe or explosion can break, so the only way down is the route the structure gives you, one locked trapdoor at a time.
Kill the two Knights
One key part each
The Beheaded Knight always drops a 
Somber Key Blade and the Resurrected Knight always drops a 
Somber Key Ring, and each of them drops a 
Metal Debris as well. Neither key half is a chance roll, so every pair you kill gives you exactly one key’s worth.
Haunted Duo Drops
There are two pairs in every kingdom, one beside the first trapdoor in the upper tower and one beside the trapdoor over the Paladin’s arena. Both trapdoors are locked, so a full run down means killing both pairs and crafting two keys.
Craft the Somber Key
Shapeless, both halves
Put the Somber Key Blade and the Somber Key Ring anywhere in a 
Crafting Table and they’ll combine into a Somber Key, no shape needed. You’ll do this twice on a full run, once for each pair of knights, so craft each key as soon as you have both halves.
A key only opens one trapdoor and is used up when it does. Use the first on the trapdoor in the upper tower, then keep the second for the one that drops you into the Paladin’s arena.
Open the trapdoor and win
400 HP, two phases
Right-click the middle block of the Somber Trapdoor with the key to open it and drop into the arena. The Paladin has 400 health and a second phase, so read its page before you go down.
The Paladin always drops the sword and a 
Corrupted Soul, with no roll on either. That means one kill is all it takes, and there’s no reason to go back down unless you want a second Corrupted Soul.
Possessed Paladin Drops
Soul Great Sword The Corrupted Soul isn’t a part for the sword, it’s the center ingredient of a 
Knight Summoner or a 
Guard Summoner. Right-click the ground with either one and you get a tamed companion that stays with you for good.
The Guard is the heavier hitter at 140 health, while the Knight has 120 health and blocks and counters. The Companions & Summoned Allies page covers both, and how to give them orders.
Usage
As a plain melee weapon it’s heavy and slow. Every swing needs about three quarters of a second to recharge, so timing matters far more than with an 
Iron Sword, and you’ll lose a lot of damage by clicking early. The extra reach helps, as you can start the swing before most mobs can touch you.
Soul Great Sword
Withered Scythe
Netherite Sword
That durability row isn’t a typo. The sword resets its own damage every time it would take any, so it never breaks. It isn’t fire resistant though, so dying over Lava can still cost you it.
If you have Better Combat installed, the Soul Great Sword counts as a claymore with 4 blocks of attack range and gets that mod’s swing animations. You don’t need Better Combat for anything else on this page.
Parrying
Hold right-click while standing normally and you enter a parry stance, which only lasts about a fifth of a second before the sword drops it again. Anything that hits you inside that window is canceled, with no damage and no knockback. Miss and you’re only locked out for a second, so you can hold right-click and let the stance retrigger while you wait for a swing.
A successful parry hits back hard. The attacker takes your attack damage plus 30% of what it was about to deal, everything within a couple of blocks of it takes your attack damage too, and you heal 20% of your maximum health, 2 hearts on a normal bar.
Nine waves of soul energy also fan out around you, each dealing 9 plus 3% of the target’s maximum health through armor, though they only hit things on the ground. Then the sword goes on a 3.5 second cooldown, longer than for a missed parry.
It works on projectiles too. The damage goes back to whoever fired the shot, not the 
Arrow, so parrying a 
Skeleton across the room hurts the Skeleton and still sets off the waves. Your tamed mobs are never caught in any of it, summoned Knights and Guards included.
Nothing that ignores armor can be parried, so that’s falling, drowning, burning, freezing, Magic, Wither and a 
Warden‘s Sonic Boom, and most of the mod’s own special damage: ghostly attacks, energy beams, gravity, void damage and the 
Swinging Axe and Spike Trap blocks in the Collapsed Kingdom. The Possessed Paladin‘s soul attacks are ghostly damage, so only its physical swings can be turned back on it.
So the parry is for swords, claws, fists and Arrows, and it won’t help you against anything that hurts through armor. That’s the gap the second ability fills, as the daggers deal the same kind of damage themselves.
Throwing Phantom Daggers
Sneak first, then hold right-click for a full second while aiming at something, and release. A wind-up sound plays just before it’s ready, and that’s your cue to let go. Release early and nothing happens, but nothing is wasted, as the 6 second cooldown only starts once the daggers are out.
Six daggers spawn in a ring around you, fly outwards, then turn after about half a second and home in on your target. The lock-on reaches roughly 15 blocks and stops at the first solid block, so you need line of sight.
Each dagger deals 8 ghostly damage, straight through armor, and isn’t destroyed when it hits. They circle back into the target for around five seconds and pass through your own tamed mobs.
The daggers ignore armor and the parry doesn’t, so the two cover each other. Armored targets like the Ancient Guardian or the Frostbitten Golem take the full 8 per dagger, and the parry handles anything fast that’s already swinging at you. They share one cooldown though, so a dagger throw locks the parry out for its full 6 seconds, and a parry that lands locks the daggers out for 3.5.
Enchantments
It takes normal sword enchantments and has an enchantability of 14, the same as Iron, so an Enchanting Table gives fair results. Skip Unbreaking and Mending, as the sword never loses durability anyway, and put the levels into damage instead.
The parry reads your Attack Damage attribute rather than an actual swing, so Sharpness adds nothing to what gets reflected. A Strength Potion does, since Strength changes the attribute, and it raises both the reflected hit and the area damage.
Tips
Stand up before a melee exchange. Sneaking is the switch between the two abilities, so crouching at a ledge and pressing right-click charges daggers instead of parrying, and you take the hit. In the Collapsed Kingdom you spend a lot of time edging around drops, which is where this catches people.
Parry the swings you can see coming. The slow, telegraphed attacks from a Haunted Knight or an Overgrown Colossus are easy to time, while a mob that just walks into you is much harder. If a boss’s hits never reflect, check whether they’re one of the armor-piercing types above before blaming your timing.
Open with the daggers rather than saving them for an emergency. The charge takes a second of crouching and needs a clear line to the target, so throw them as you come around a corner, not when something is already on top of you.
FAQ
It only comes from the Possessed Paladin, which sits in the arena under the Somber Trapdoor in a Collapsed Kingdom. There’s no recipe and it’s never in Chests. Kill both pairs of Beheaded Knight and Resurrected Knight for the key halves, craft a Somber Key from each pair and unlock both trapdoors. The sword always drops, along with a Corrupted Soul.
Every time the game tries to damage it the sword resets its own damage value, so it never wears down and never shows a durability bar. That makes Unbreaking and Mending pointless on it, and you’ll never need the 
Netherite Ingot it lists as a repair material either. It can still be destroyed as a dropped item though, since it isn’t fire resistant, so Lava will take it.
Usually one of three things. You’re sneaking, which charges daggers instead, or the hit is armor-piercing damage like fall, fire, Magic or the mod’s ghostly attacks, which can’t be parried. Or it’s timing: the window is only about a fifth of a second, so hold right-click and let it retrigger rather than tapping.
Each of the six daggers hits for 8, and because it lands as ghostly damage it goes straight past armor. They also aren’t used up on contact, so a dagger that stays locked onto something can strike it several times across the five seconds or so it’s in the air. That makes the total very dependent on whether your target keeps moving away from them.
