This is my take on Nimis CoC Fireball inspired by AllanYM and Palsteron. Links to their build guide videos below.

POB: https://pastebin.com/nWHZi70z

Offense: 613 million Guardian DPS

Defense: CI, 5k es, 62k armor, VMS, 4 Endurance Charges, Aegis, es leech and on hit, 84% max res, Glancing Blows max block, stun immune

Description:

The build abuses the interaction between Nimis, Fireball, and Sniper's Mark to ensure all 13 projectiles (4 from fireball itself, 9 from sniper's mark) from each cast shotgun single targets for massive DPS. We trigger Fireball with cyclone for 10 casts a second. Scaling sniper's mark effect is very important in this build since every 20% mark effect gives us an additional projectile. We go CI with Aegis Aurora and Melding of the Flesh for very strong and completely unnecessary defenses. We also have massive recovery with ES on hit Watchers, ES leech from cluster notable, ES on block with Aegis and a bit of ES regen.

Pros:

• Massive DPS combined with super tankiness
• Very high ES recovery from multiple sources
• Smooth cyclone gameplay that allows movement while casting
• Very high cyclone movespeed with Mageblood, elusive, tailwind, onslaught

Cons:

• Mageblood required
• Very expensive gear. I spent 425 divines excluding MB with some lucky self crafted pieces.
• Clear is above average but nothing to write home about
• Without the +1 Power Charge relic I'm using, your damage will be lower

Why Ascendant?

The other versions of this build are Deadeye and Pathfinder. Those versions have more projectiles and chain but struggle with getting crit capped. This build solves crit by stacking power charges. Ascendant has the Unleashed Potential Forbidden jewel that gives your +1 power charge, along with +1 endurance charge and 50 second charge duration. This allows you to make use of Enduring Composure notable from small cluster for permanent 4 endurance charges. Before a boss fight, you can pre stack the endurance charges by casting Forbidden Rite on weapon swap.

Ascendant Occultist and Deadeye give you 35% sniper's mark effect combined, which is not as good as Deadeye 75% mark effect, but you also get stun immunity, permanent tailwind (which allows you to get elusive and elevated onslaught on boots), and more passive points. Ascendant also allows for more flexible passive tree pathing to reach all 3 power charge nodes, overall making a more offense/defense balanced character at the expense of projectiles and clear.

Disclaimer:

This build is not meant to be a low budget or accessible. It's an end of league currency dump showcase that can faceroll all content with a completely unnecessary level of power. GLHF!

AllanYM version: YT Video Showcase

Palsteron version: YT Video Guide