This actually unlocked from me after clearing Blizzard difficulty but I will share my build if anyone is struggling. I had breezed through the other difficulties but Blizzard needed a build with really good synergies for me to do any damage whatsoever.
I am going to assume that you have already unlocked all upgrades from the blood soul vendor and all items in the skill trees
Sect: Infinite Arhat
Sub-sect: Sunburst
Core Relic: Azure Dragon Spirit
- The True Damage is what we want from this. Enemy defense is so high on this difficulty you need to do True Damage to even hurt them
Power Relic: Vermilion Bird Spirit
- Try to get this legendary but epic is ok. This is needed on this difficulty because the enemy defense is so ridiculously high that without True Damage you just can't hurt them. Try to refine as many relics as you can to boost the damage bonus
Agility Relic: Galesteps
- The most important aspect of this build. It allows you to dash around and essentially always have your sheath skill ready or nearly ready
Skill Relic: A few options
- I typically picked Heart of Hatred for this to max out damage. The defense loss doesn't really matter if you have the build right as you'll be doing so much damage you can't really get hit. If you do, try to get one or two lifesteal skills during the game.
- Saberstone is another good option but I preferred the guaranteed damage boost of Heart of Hatred. If you find yourself dying too much this could be a good option for you
- Alien Stone is the best if you are really struggling with dying. The defense boost is ok but at legendary rarity it gives you one free hit without taking damage if you can avoid damage for 10s. I originally went with this for my build but found the damage boosts to be more helpful in the end
Weapon: A few options
- I found that swords don't really make too much of a difference so didn't put any effort into respecing them or changing their rarity. Ranged/All Damage+, Sheath Cooldown- and Ignore Defense+ are the most important specs.
- Best options: Fallen Sun and Sudden Rain. These are exclusive to the infinite arhat sect and therefore synergize really well with it. Between the two, Fallen Sun is better especially at Mythic rarity. The AOE attack is really good for taking down mobs and dealing additional damage. The damage boost of Sudden Rain is also good. Both offer guaranteed ranged damage boosts so take whichever has better specs for the other stats
- Good options: Hawkeye, Ancestor, Common. These all offer good generic damage boosts but they're not as good as Fallen Sun or Sudden Rain. If you get one, just keep it unless something with better specs shows up
Skills
- There are a lot of skills but there are a few that are critical to this build. Total Madness is one, the 300% attack bonus is pretty much needed. There is a skill that gives you 1.25% damage boost per 50 blue souls that is also really good. Bullseye is also really good. Sword God, Sword of Heaven or Arc Light Blade are all good as well. Other than that, mainly focus on skills that boost damage, specifically Flying Sword or True Damage and also add ignore defense. Also try to get one or two skills that heal you if you don't have better options
As for rooms, I ranked them like this
1) Skill book room (purple book)
2) Strong enemy room (red skull) - this could have a skill book so risked it
3) Relic room (green chest)
4) Sword room (yellow sword)/Blue soul room (blue flame) - depends on if I needed a sword or not
5) Health room - never needed extra health with this build
At the beginning of the game, a relic will drop on the ground. I kept restating my game until I got one of the ones in my list as a legendary one. You also can pick a relic from the relic book so once I got one I wanted from the random drop I would pick another from there. If I didn't get Galesteps from the drop I would pick it from the book, it's essential to this build. I'd then hope for one of the high damage skills from the free skill book too.
Whenever your refine a relic, always pick damage. If you have the skill that boosts damage based on blue souls don't buy relics unless you have more than the cap (12000). If you don't have that kill. Buy relics from the vendor even if you don't need them and refine them to attack bonus.
Always take blue souls and a relic from the merchant at the transition station.
With those stats, my general strategy was to try and always have sun piercer active and to just dash and shoot flying swords from a distance. If I didn't have it active, I didn't bother to charge my flying sword attacks, I just fired them in the hopes of triggering the Sword God, Sword of Heaven or Arc Light Blade skills (if I had picked them up yet). With this, the bosses were still a little longer than normal because of their health but still gave me no problems. If you see a heluo tentacle pop up, run away until they smash and the return. Also, you don't need to kill the flesh blobs that spawn to clear a room so don't bother if you don't need to.