Failed Champion

After acquiring the Dream Nail, upon returning to where the False Knight was fought, the corpse of the Maggot that occupied the armour is found in the room above the arena, along with two living Maggots mourning over it. Striking the corpse with the Dream Nail will transport the player to an arena where they will fight the Failed Champion.

The Failed Champion uses the same attacks as the False Knight, however it will spam its attacks near constantly and contact with their body or mace does 2 masks of damage. The shockwave itself and the rocks do only 1 mask of damage.

In addition, rocks will fall during every attack and the shockwave from the Slam is much taller. It gives 300 Essence when it is defeated.

Tactics
Since hitting the armour doesn't give any SOUL and the Champion attacks relentlessly, allowing little time to heal, it is recommended to use Joni's Blessing, Stalwart Shell, Quick Slash and an aggressive strategy. With this setup and a decently upgraded Nail, it's possible to damage-race the Champion. Fragile charms also work well as they don't break when dying in Dream fights.

Alternatively, the fight will be easier if the left Maggot is left alive until the Champion is defeated (as they do not respawn) - if the player loses in the dream fight, they wake up with full health but no SOUL. Using the Dream Nail with Dream Wielder on the Maggot is a convenient way to re-enter the fight with full SOUL.

The Desolate Dive/Descending Dark spell is effective as it hits twice and the invincibility frames allow the player to dodge mace strikes while casting.

His jumps are wide and provide room to be dashed under. This will create an opening to attack him from behind and dodge his smashing attacks. This is more effective with Shade Cloak equipped.

Another reliable opening to attack is when he jumps backwards, as this jump never lands with smashing attack.

During one of the Champion's Rage moments is the best time to use Descending Dark as the player can then flee without taking damage.

Never try to heal during normal attacks, unless using Quick Focus or Shape of Unn, as the Failed Champion closes distances very quickly.

Dream Wielder shines in this boss battle. While it is almost impossible to gather enough SOUL from the Failed Champion to heal reliably through conventional means, when it falls, there is time to Dream Nail him three times before attacking. Then, while the Champion is Raging in the middle of the room, heal with Quick Focus.

Another, easier way is rather cheap. Use the charms Weaversong, along with any others you may find useful, such as the Dreamshield to block meteors, although only this one is needed. When you engage, quickly jump and, using Mantis Claw, hide in the top right or left corner. Charge the super dash using Crysal Heart but don’t let go, so you stay in place. From here, let your minions slowly pick away at the boss. If a meteor hits you, immediately jump back up and charge the super dash. Make sure you are out of its reach. After waiting a while, you should be able to slowly chip down all his phases easily.

Trivia

 * The armour and the head have separate health values.