Evolutions
Dreadful [Reach], Echoes of [Rage], Preference, Chain Shatter
TLDR for those that aren't nerds
Chain Shatter is the only Evolution 5 worth using, yes you can use Berserker Fury instead of Primed Fury, use [Spring-Loaded Blade] if you don't own [Primed Reach].
Shard Talk
This weapons gimmick is incredibly buggy. The gist is you hit an enemy, it plants a shard. If you plant a shard on a different enemy, every shard that existed at that moment does damage to it's host. Shards are not planted by status damage, nor hits from Melee Influence. Slam radius cannot plant shards.
They NEVER benefit from; Status Damage (Elementalist), Body Part Multipliers, Melee Duplicate, Modded Crit Chance sources, Arcane Crepuscular, Melee Animosity, Weapon Damage (like Arcane Arachne or [Vigorous Swap]), Faction damage, Extra Hit abilities (such as Toxic Lash or [Xata]'s Whisper)
They have stats of 0% Crit Chance, 1x Crit Damage, 0% Status Chance. This means if you want them to crit, you need flat crit chance sources. Same with Status Chance (though the only source of flat status Chance you can use solo for [Thalys] would be [Proton Snap]).
For whatever reason if you have Secondary Fortifier equipped on your secondary, shard damage generates overguard.
Without detonating shards via Chain Shatter heavy, shards only benefit from Base Damage (excluding [Condition Overload]), Crit Damage (only with flat Crit Chance sources such as Wrathful Advance). Insanely bad.
The Wonderous Chain Shatter
When you detonate with a heavy via Chain Shatter, it magically makes the shards lock in. It allows them to scale with [Condition Overload], Elemental mods, lets them use the weapons Modded Status Chance (this in combination with getting elemental mods allows them to proc modded elements). Rather than shards detonating once as you would expect, they detonate for every hit the heavy does (first heavy is 3 hits, essentially tripling shard damage). It also randomly gets an 8x Damage multiplier, making shards detonated via Chain Shatter do 24x the expected damage.They sadly ignore combo multiplier. The shards explode in a 5 meter radius when detonated by Chain Shatter, detonating any shards on enemies hit by this aoe (mimics the damage the shards did on the enemy you hit with the heavy). Everything stated above makes Chain Shatter by far the best evolution for a Tennokai setup.
The Unexciting Explosive Growth
Explosive Growth isn't really anything special. Every time the shard grows it does damage to the host, until the third where it impales and does double damage. The impale doesn't trigger Melee Afflictions. Effective 4x compared to no Evolution 5. Very boring.
The Abhorrent Void Splinters
Void Splinters is by far the weirdest one, and it's also horrible. The shards no longer leave after damaging the host, causing them to linger. The halved damage is a final multiplier. The Crit Chance bonus, listed as 100% Crit Chance, is actually split into 2 different Crit Chance modifiers. One that gives flat Crit Chance, approximately 35%, with the other 65% being multiplicative Crit Chance (meaning it multiplies your Crit Chance after mods and final effects such as Arcane Avenger or [Cat's Eye]) This sounds enticing (there's only 1 other source of multiplicative Crit Chance in the entire game) until you read the fine print, which is a few problems with the evolution. In order to get the Crit Chance bonus, you must hit EXACTLY the shard. It quite literally becomes a part of the enemies hitbox. This leads to issues with certain weapons, as an example I could never get it to function on any beam. This also leads to about half the spots that shards can generate on enemies being completely impossible to hit, at least on bipedal enemies. Despite being listed as "weak spots" by the evolution, hitting it does not grant any weakpoint multiplier, headcrit multiplier, or charge incarnons. The shards are quite small, and it's very unpractical to melee an enemy then attempt to both locate and hit the shard during real gameplay. The shards do not benefit from the Crit Chance. Interesting premise, mediocre in practice.
Mod Choices
Melee Influence is the meta. Depending on who you ask, it's incredibly boring since nearly every melee uses this damn arcane. I'm using it here because I enjoy the arcane, though I have found success using [Thalys] as Gas with Melee Vortex. They complete essentially the same job, both kill everything within around 20m, just Melee Influence doesn't check for Line of Sight, has better uptime, etc etc. Pick your poison.
[Condition Overload] is extremely bugged on Heavy Scythe First Heavy (the spinny one), scaling off a value of 600% instead of the actual value of 200% for all 3 hits. This makes it 3x stronger than intended, along with just being the usual best option for light spam/Tennokai melees. Easy slot.
Despite getting a whopping 40% Attack speed and 5m of Range from evolutions, [Primed Fury] and [Primed Reach] still make an appearance. If you haven't logged in enough for [Primed Fury], you can make your choice Between [Quickening] and [Berserker Fury] as replacements. [Galeforce Dawn] is horribly slow, and with most of our damage being within heavies we want to [Reach] Tennokai opportunities faster. [Primed Reach] brings us to about 11m of Range, allowing shards to be spread from very far away and making the melee feel great to use. Due to the horrible [Follow Through] of the Heavy Scythe weapon class, as enemy density scales the shards are more and more of our DPS, ranging from about 16% at one enemy to 30% at 20. Basically, the shards are not slackers at all.
"If the shards don't use modded Crit Chance, and therefore can't crit without flat sources, why are [Galvanized Steel] and [Blood Rush] here?" you could potentially be pondering. On top of the vast majority of our damage output not being from shards (if you look at the damage on 3 enemies at least), there's simply not much else to slot. Base damage is more than covered by [Condition Overload], Status Chance by [Weeping Wounds], and double slotting Attack Speed doesn't make too much of a difference for the forward light combo (the only one worth using on [Galeforce Dawn]).
[Weeping Wounds] needs no introduction, or explanation. Just gives a truckload of Status Chance. Essential mod for 12x Tennokai (the template this weapon uses, and what this build is! Every melee build looks like this currently, though on other weapons it's optimal to use Smite mods over [Galvanized Elementalist])
[Shocking Touch] is used over [Voltaic Strike] due to having obscene amounts of Status Chance already from [Weeping Wounds] and Galvznized Elementalist (even without [Galvanized Elementalist], [Shocking Touch] is superior). The Electric part of a Melee Influence build.
The Fabled Gas Vortex Variant
If you don't enjoy Melee Influence or would rather a slightly worse weapon in exchange for being able to dodge the meta, switch [Shocking Touch] for [Primed Fever Strike] (toxin % doesn't buff gas status damage, but improves weighting as well the raw damage), [Galvanized Elementalist] for [Volcanic Edge]. If you won't have an external source for Magnetic Statuses to actually benefit from Melee Vortex (companions can do this very easily!), you'll need to lose some Attack Speed and slot Magnetic Rush over Primed Fury/[Berserker Fury]. Despite the low weighting, magnetic procs are still rather consistent due to the [Thalys] having a pretty alright base Status Chance.
The insane damage scaling from [Condition Overload] on the first heavy allows you to make Gas clouds that can actually kill things. Gas is slightly cooler than Electric, though if you don't wish to lose Attack Speed due to slotting over [Primed Fury], or to not lose [Galvanized Elementalist] you can keep [Shocking Touch] and not slot [Volcanic Edge]. Their performance is similar.
Conclusion
This is probably the single buggiest weapon in the entire game. There's 0 logic behind what shard damage does and doesn't scale with, or why Chain Shatter allows it to use certain mods it didn't before, or why Void Splinters Crit Chance buff is the way it is (I lost a week of sleep over it). This essay is the culmination of tens of hours sitting in the Simulacrum, getting feedback, notes, testing from other players (the radius of Chain Shatter was tested by an anonymous Wiki comment. Chain Shatter allowing shards to proc statuses, allowing elemental mods and [Condition Overload] to function as well as overguard generation all came from comments under Kyaii's video on [Thalys] and my testing after reading them). The message of this story? This game sucks.