No archon shards required, though I like 2 Energy Max archon shards for better use of Arcane Energize.

My [Chromatic Blade] uses corrosive only.

Preferred energy color is electric to add towards corrosive damage on the [Chromatic Blade]
OR
Heat for heat procs and because it contributes towards max health from Elemental Ward.

Electric for Elemental Ward isn't the best, but the damage [Reflection] multiplier is a nice bonus.

Cold is also good for a big armor bump, but will add cold procs to [Chromatic Blade], which isn't the best, but its fine.

Would not recommend Toxin while using Elemental Ward because its not as useful as the other 3.
If you're using viral on [Chromatic Blade], and using a different Helminth ability, toxin is just fine.

This build can kill anything including high level SP, but is also fun when doing stealth missions or just wanting to open enemies to finishers.

Fun notable melees would be Pangolin Prime, Innodem / [Rumblejack], Ghoul Saw :)