This build was my take on making something which didn't stick to the usual meta of viral+slash.
I also wanted to make it viable for the steel path, which it is.
This means putting in a double heavy attack on enemies and allowing the tick damage to kill them.

For a build based around higher single target damage see the link below:
https://overframe.gg/build/60181/karyst-prime/covert-lethality-finisher-build/

Damage type Explanation:
The use of gas makes this build better against large groups of enemies.

The gas damage doesn't tick past shields or armour, but is good against grouped enemies. (The initial hit will remove most of the shields and any gas/slash procs will take care of the remaining shield and health).

Slash does not go past shields, but once the shields are gone (most likely with the initial strike) the combined gas and slash will [Shred] health as it ignores armour. A guaranteed proc of slash comes from the first hit of the heavy attack (The attack from left to right).

Mod Use Explanation:
Mainly this build is a typical heavy attack build (corrupt charge, killing blow, amalgum organ shatter) but there are some different mods used

• The Sacrificial mods are both used to give the maximum crit bonus on heavy attack (+550% crit on heavy attack when sacrificial steel is maxed)

• Primed Fever Strike is used to get higher damage.

Replacable Mods:

• The Sacrificial mods can be replaced with True Steel and Pressure Point

• Primed Fever Strike can be replaced with normal fever strike.

• Amalgum [Organ Shatter] can be replaced with normal organ shatter.
  This will result in the setup not being as effective, but will still be relatively good.

• [Volcanic Edge] can be replaced with [Healing Return] to give good healing capabilities, without having to use a certain frame (This will result in less gas procs, and slightly lower damage, but it should still perform well enough.)

How to obtain the rarer Mods:

• Sacrificial Mods - Complete the sacrifice quest

• Primed Fever Strike - Can be obtained from Baro Ki'teer (Not guaranteed to be brought by him every time, but will turn up every so often)

• Amalgum Organ Shatter - Can be obtained from the Thermia Fractures event at 50 points.
  Warframe Synergies:

• Inaros - He will tank pretty much everything, so you won't have to worry about dying.

• Chroma - Also pretty tanky, but also offers a damage buff

• Ash - If you make a build based around his invisibility you won't die. His passive will add bonus damage and duration to the slash proc given in the heavy attack.