So I really like Fury Valve; it's been an amulet I've wanted to build around for ages. However, it's been tricky to find a way to make it actually an advantage, especially for single target damage. I spent a whole day testing every projectile in the game with Fury Valve, and finally found a skill that takes advantage of it properly; Spectral Helix.

Essentially, Fury Valve lets us take a Helix projectile and any added projectiles and use those, in conjunction with Return (through the support or a Nimis) for a massive damage multiplier. For bonus projectiles (and damage), we use Sniper's Mark. Why does this work?

Step 1; fire one Spectral Helix projectile. Usually Nimis makes them fire in a random direction (which is why most other projectiles that use both Nimis and Fury Valve don't work), but Helix just spins in a circle, so this disadvantage is negated.

Step 2; it hits an enemy that has Sniper's Mark on it.

Step 3; it stops spinning and splits. I'm using a Deadeye, which gives +2 projectiles, as well as the notable on the tree which gives +1 for attacks. I have 2.11x mark effect, so lvl21 Sniper's Mark gives 10 projectiles. Fury Valve gives +2 inherently, so 15 copies of my Rakiata's sword fly off into the distance. This could go higher; if I were using claws I could get at least two notables that give +1 projectile to claw attacks. I could also use the +1 projectile tattoos, and in theory have both of them doubled by Warrior's Tale, so in my view the theoretical max here is 21 splitting projectiles.

Step 4; they return to sender. Assuming I'm standing near the enemy, all 15 projectiles return and smack the enemy for full damage, multiplying the one Helix projectile's damage by 15.

I at first thought that the split projectiles wouldn't all be able to hit one enemy, but turns out they can; I tested this extensively. I suspect this is because Helix projectiles can innately hit targets more than once due to their bouncy behaviour, so this transfers to the splits as well.

Here's my prototype Deadeye character which I run through a t11 City Square map here: https://youtu.be/Zj8nZgkL5Tw. (This is my first video so please forgive any rough edges on it!). Here is my PoB as well: https://pobb.in/tDaxg2Nfv3zf

I'm currently using a Rakiata's Dance sword since it really is tremendously good damage; with 15 projectiles I'm estimating close to 10mill dps, and this character is only just lvl80. (It's also incredibly squishy which is why I didn't run a t16 map). (The secret bonus of using a two hander is also getting to use the mtx in the video which leaves these great green trails behind)

I will be trying to make this into a proper build that can do t16 maps, guardians etc. without dying to a stiff breeze, but that's kinda tricky with a Deadeye. I started this project with Deadeye becaue the mark effect, extra projectiles and Far Shot are all very synergistic. However, I'll likely also try an Inquisitor build using Energy Blade, partially because it'd be a lot tankier, and partially because who doesn't like to see tons of lightsabers flying around. If anyone's got any ideas for this combo (or advice on how to make a Deadeye that isn't a wet paper bag), I'd like to hear it.

tl:dr; Deadeye using Spectral Helix, Fury Valve, Nimis and Sniper's Mark multiplies projectiles by at least 15 and smacks enemy with all of them, leading to tremendous damage increase.