The final upgrade path within Draconic Evolution is Chaos; this will require you to kill the Chaos Guardian a few times. Killing this dragon is no easy task and will require a whole bunch of prep work. Hopefully, you have upgraded all of your equipment.
This dragon can be killed more than once; once killed, you can access the cavern below the dragon where you can harvest the Chaos Crystal.
This is no easy fight, you will die (unless you know what you're doing), and it will require a lot of power. There are a few things you should do before attempting this fight.
To begin, you will need to fly out 10,000 blocks from the End island (in any direction) to get to the dragon’s arena.
Just like the Ender Dragon, several crystals are scattered around the Chaos Island that will heal the Chaos Guardian and make it immune to damage. Each of them has 50 hearts of health and, when hit, gains a shield that makes the damaged crystal immune to damage for a random duration between 5 seconds and 10 seconds. Hitting a crystal while it is shielded will refresh the shield's duration.
The Chaos Guardian randomly alternates between 4 movement behaviours, which are:
Circling around the centre of its island, attacking nearby players
Circling around the closest player and attacking it
Charging at its current target, dealing 50 hearts of damage on contact which bypasses armour, then going back to the centre of the island Fleeing from nearby players
While doing this, it also randomly alternates between 6 attacks, which are:
Going to the centre of its island and standing there, quickly firing fireballs at nearby players, each dealing up to 2 hearts of damage in an area on impact and causing a small fiery explosion. Players further from the impact take less damage.
Charging at its target, but also continually firing the same fireballs as the previous attack at its target while doing so. Firing a volley of homing fireballs on its target, dealing up to 2 hearts of damage in an area. Firing a volley of homing cyan energy balls on its target that can pass through walls, each dealing up to 3 hearts of damage in an area that bypasses armour.
Firing a volley of homing dark red chaos balls on its target that can pass through walls, each dealing up to 3 hearts of damage in an area that bypasses armour and splitting into 3 to 5 smaller chaos balls that deal the same damage on impact. Each hit from those chaos balls also drains 30 000 to 40 000 Redstone Flux from any draconic armour the player is wearing.
All of these projectiles have five health and can be destroyed, and their explosions ignore damage immunity. They are also able to damage and kill players in Creative mode.
The Chaos Guardian will also periodically fire green balls on nearby dead crystals, restoring them to full health.
When below 20% health, the Chaos Guardian automatically switches to its fleeing movement. In this state, it will attempt to restore crystals much more often, will no longer attempt the fireballs attacks, and instead fire a volley of black projectiles that will teleport the player away if they are hit, dealing ten damage in the process. Upon regaining enough health, it resumes its normal behaviour.
Attacking the crystal currently healing the Chaos Guardian will cause it to immediately switch to its fireball charging attack or to its chaos ball attack if the crystal was destroyed or the Chaos Guardian is in its fleeing movement.
Lastly, the Chaos Guardian takes 75% less damage on parts of its body other than its head, and any single damage instance it receives exceeding 50 hearts of damage has the exceeding damage reduced by 30%.
On its death, the pillars of all crystals collapse and the Chaos Guardian goes to the position of the Chaos Crystal it is guarding, dropping its Experience there.
Lightning will then continually strike above the Chaos Crystal's chamber until it is harvested. Breaking the crystal causes the island to detonate 35 seconds later. This detonation will kill anything and everything on the island, even players in creative mode.