Psyker
25-40% Cleave on Hit. Stacks 5 times.
Hitting at least 3 enemies with an attack, quells 2-5% Peril.
4.5-6% Close Range damage on Repeated Hit. Stacks 5 times.
1-4 Burn Stack(s) on Critical Hit to a maximum of 3-12 Stack(s).
TLDR: this is a high mobility high lethality wave clear machine.
This build efficiently turns all peril into toughness ASAP through mega cleave melee + crack of bone + tranquility thru slaughter (which quell) which powers quietude (quell == toughness) when in melee. I've kept warp splitting so that you can max peril assail with warp unbound and occasionally get some super big cleaves melee. Your damage comes mainly thru triggering SG and being able to stay in it permanently while in the middle of a horde. No horde can kill this build absent serious misplay.
Hordes you want to fight with the lights. Elite stuff you want to push attack into heavy spam for the poke and then strikedowns. You can also go straight into heavy strikedowns but it's not as dangerous as the PA poke -- it is however quicker to access. Always aim for heads.
Your secondary toughness gen options are assail and warp slice which generate warp kills that feed you through soulstealer (warp kill == toughness). It's good to mix assail in with melee to keep malefic momentum up. Make sure you are stutter stepping when using assail so that guns can't hit you easily.
No warp rider because you aren't going to be at max peril most of the time. If you want you can drop some stuff to get it but IMO the damage gain isn't as big as the losses you'd take in other areas and you'd want to rejig for a max peril build with unstable/wrath/warp rider and give up warp speed and crack to get there. You'll lose a ton of durability from the melee quelling but gain a lot of damage while at max peril.
Movement should happen with laspistol out as it makes you a lot faster. Laspistol + DD trigger + SG turns you into a mega speed demon. You can easily outrun a lot of very dangerous threats by swapping over and then sprinting and sliding with the pistol, it's a big advantage so work that into your routine.
Blocks, pushes and push attacks are a big part of the power of the build and the mk8 flow so be sure to take advantage.
The stam token and stam regen allow you to sprint longer and allow you to not collapse when you're at max peril from SG and a rager pack jumps you (meaning no kinetic deflection). It is a VERY bad idea to hit SG when engaging ragers as you can't use your push without risk of periling out. You don't need damage vs rager packs, you need patience and blocking endurance and the push attack which this build has in spades.
You can efficient use the push attack poke on the mk8 to clean up individual crushers but for bulk crushers run away and gun em down with the laspistol fire while in SG. You can technically sword them down in bulk but it is risky and odds are you will get krumped so why take the risk.
Assail is used for general assail stuff. In addition to the melee weaving mentioned above you can also use it to shred ragers packs and mulch gunners which you should do.
Works in havocs just fine if you have a bubbler into the low 30s, beyond that the cleave situation gets dicey and you can't mulch hordes as efficiently. Extremely effective in aurics, you can carry and clutch very easily so long as you stay mobile.