First of all, I would like to thank my boys. Owen Tseng, JOJO, big brain time just before league. Hoeji, the tester. And GTO59673, the finance supporter.

Here's my test result of reduced projectile speed spectral helix.

https://www.youtube.com/watch?v=_B7qZULkVjc

Spectral helix can always spiral up to 4.25 rotations, and the projectile speed does not affect the rotation distance. In my test, I found the number of total hits versus projectile speed was limited to 36 hits against this little totem. Further, the hit rate decreased to around 0.5 hits per sec at -99% projectile speed. This indicates the mechanicsm is far complicate than spectral throw that noted hit enemies every 0.3 sec.

Herein, I found helix projectile can only hit a enemy once everytime it slightly slightly moves a little distance. This suggests that helix has to travel a minimum distance to cause a hit. Hence, I proposed these mechanic notes.

1. Figures below demonstrate the helix travel route with pink line, monster hit box with blue circle, and the helix hitbox of red dot circle, assuming the distance between character and monster is 0 for optimization.
2. The first hits and last hit projectile are denoted as hit start and end (red cross). Everytime a helix projectile hits a enemy, the position is denoted as hit point (red dot). Because of the minimum distance to cause a hit, the total hit of spectral helix per cast has a maximum.
3. A helix projectile has a minimum traveling time (or hit rate) between each hit points of 0.3 second. The traveling time between each hit points also scale with projectile speed. (really obvious in -99% projectile case)

https://preview.redd.it/rj9wy69q03k91.png?width=499&format=png&auto=webp&s=bec4f6e84529e344a610c35e40c70f6a168f90a7

https://preview.redd.it/umw40ovd13k91.png?width=597&format=png&auto=webp&s=7208c4a4a36a4c01e2c66ef812456d6af961df2f

Base on this pov, it is obvious to conclude that spectral helix with reduced projectile speed has a efficiency "Sweet Spot". This is because the high projectile speed leads to longer travel distance between each hit spot, as if the helix skips the hits. On the other hands, too low projectile speed ends up with bad hit rate. According to my testing, best projectile speed of spectral helix woud be at -93% to -95% that effectively hit monster with basicly all hit point and good hit rate.

Here is Hoeji, the tester, second place in 3.18 Gauntlet Scion, demonstrating his lv82 impale helix with precise technique slayer melting down Baron within 3.5 sec with only 700DPS axe.

https://www.youtube.com/watch?v=zsanUcBS5YI

His current POB: https://pastebin.com/aabtCQRK

Finally, lets talk about how to reach the -95% projectile speed. Pretty simple. Spam veiled chaos on simplex amulet until you hit good roll of projectile speed. 20Q of accelerating catalyst, and then throw it into the lake! Higher difficulty of Reflection of Kalandra would result in higher modifier multiplier.

My amulet showcase:

https://preview.redd.it/xbov33vz73k91.png?width=411&format=png&auto=webp&s=6db040c68dc17a38819bb669878d55ab3c531a97

This is the result of difficulty 14 Reflection Kalandra. With the Adjacent Animosity node and some jewels with little projectile speed, it is fairly easy to reach just the right sweet spot. Nothing too special. DEXDEADGE

I know this could be a busted skill that soon everyone play it. But who knows? Just enjoy it!