Quick answer: The three Ritual Cauldron fragments combine into the Restored Ritual Cauldron. Rest at a bell, go to Upgrade Equipment, pick the Juggernaut, press P, and keep Space held. The cost is 5,000 Remnant Dust.
What you need
To Soul Temper the Juggernaut, have a Restored Ritual Cauldron on hand along with 5,000 Remnant Dust.
You get the Restored Ritual Cauldron automatically after collecting its three fragments; no crafting is needed. Each fragment is found in the Mountain of Imprisonment. The item card displays “Used to Soul Temper the Juggernaut.”
In Phantom Blade Zero, the forge cave beneath the bell at Iron Butcher’s Camp contains Ritual Cauldron Fragment I.
Fragment II is at a camp beneath the Cavern Passage bell. Completing The Broad Saber gives you Ritual Cauldron Fragment III.
How to Soul Temper the Juggernaut
Rest at any bell. From the bell menu, choose Upgrade Equipment.
Stay on the MAIN WEAPONS tab and pick the Two-Handed filter, which is the fourth icon. Select the Juggernaut from that list.
Use P to open Soul Temper mode. A purple screen appears, showing the Restored Ritual Cauldron under Owned and Cost. Beneath it, the button reads “HOLD Space TO SOUL TEMPER” and displays a cost of 5000.
Keep Space held until the process finishes. The message “SOUL TEMPERING COMPLETE” appears; the Juggernaut’s name changes to purple, its Soul Temper badge appears, and Unfading Sunset lights up. The 5,000 Remnant Dust is deducted at that point.
What Soul Tempering does to the Juggernaut
Soul Tempering unlocks the Juggernaut’s Unfading Sunset effect. It reads “[Crimson Wheel Slash] no longer consumes [Red Edge] when it hits an enemy marked with [Bandit-Slayer Mark].”
The Soul Temper doesn’t touch the weapon’s base numbers. Damage stays at 288 and Guard Break stays at 114.
Normal upgrades still work the same way afterward. Going from level 1 to level 2 raises Damage from 288 to 317 and Guard Break from 114 to 126. That upgrade costs Broadplate Metal x3, Solvent x1 and 1,170 Remnant Dust.
More effects unlock as the Juggernaut levels up. Blood-Fed Edge arrives at level 5 and reads “If a hit is taken while performing [Crimson Wheel Slash], the attack becomes more powerful.” Sunset-Stained Edge Lv. 1 arrives at level 10 and reads “Slightly increases damage dealt by [Crimson Wheel Slash].” Restless Wave unlocks at level 15.
