I have been testing out The Hidden Blade and I think there is a lot of hidden (hehe) potential with it, and I want to throw out what I've learnt and some ideas for theorycrafting.

Firstly, I want to clarify a few things about Unseen Strike (which is the unique skill from the Hidden Blade), since the wiki has a few major inaccuracies.

• The wiki states that "If using 2 weapons, it will alternate between each weapon every time you gain phasing". This is wrong, Unseen Strike only ever uses the weapon in your main hand. It never uses your off hand weapon. This was tested using a Mjolner in the main hand and Hidden Blade off hand, every hit from Unseen Strike triggers a socketed lightning spell. It is also wrong in PoB, where it incorrectly assumes that the weapons alternate hits.
• The wiki states "If triggering Unseen Strike on a different weapon, the game will check that weapon's support gems instead of The Hidden Blade". This is also wrong, Unseen Strike is only affected by gems socketed in The Hidden Blade, whether its in your main hand or off hand. If you have an off hand Hidden Blade and a different main hand weapon, socketing GMP in your main hand weapon will do nothing to Unseen Strike, GMP will need to be socketed in your off hand Hidden Blade.

With what we have learnt, I have been theorycrafting a few ideas with the Hidden Blade.

• Automated Shock Delivery for 1-button Lightning Conduit:

We use a MH Mjolner socketed with (anomalous) Shock Nova, Overcharge, and Unbound Ailments. We combine this with an Astral Projector for the Shock Nova. This will trigger Shock Nova almost every time Unseen Strike hits an enemy (there is a 0.25 s cooldown). We also get at least +1 chain from Mjolner, since it applies to Unseen Strike. Thanks to the Astral Projector, this will drop the Shock Nova right at the enemy's feet whenever they are hit with Unseen Strike, and Shock Nova guarantees a shock. Now all that is left is to self-cast Lightning Conduit. In theory, this should give us more damage compared to CwC LC setups (which is the other popular 1-button LC build), since we can dedicate a full 6-link to LC. Here is a very barebones PoB for the concept https://pobb.in/W0IKtdAVOI5m. I'm going Inquisitor to help meet the requirements for Mjolner, and go for crit based LC. Please let me know how this can be improved as I'm not good at making builds

• Cameria's Avarice Autobomber:

The main thing I'm trying to take advantage of here is that any global modifiers to projectiles affect both Unseen Strike as well as the projectiles from Icicle Burst from Cameria's Avarice. We can freeze everything with Expedition's End, Heatshiver for more damage against frozen enemies, and stack as much cold to fire damage from the support gem and Pyre (we already have 100% phys to cold from Icicle Burst). We top it off with Gloomfang for non chaos as extra chaos, and go elementalist to let it all ignite. This could be interesting with the new Nimis ring, as it will affect both Unseen Strike and Icicle Burst. I've tested with Vengeant Cascade and it does indeed work for both projectiles. Here is an even more barebones PoB https://pobb.in/z6aI_9TakWJP. TBH I don't think this is all that good, but just wanted to share the idea.

Some other ideas I haven't explored as much but might be worth looking into:

• People have used Mjolner + Ball Lightning as a delivery mechanism for Corrupting Fever
• Unseen Strike has a rather high Attack Damage and Added Effectiveness of Damage at 250%, which would be great for stacking flat damage or with high base damage (something with Rebuke of the Vaal or Paradoxica maybe?)
• Frostbreath might be good too, since we can guarantee chill from the mace mastery to always get double damage
• Might be some cool stuff we can do with the new Nimis ring, but also want to throw out Kineticism and Fury Valve as potential ideas (Kineticism would prevent fork, pierce and chain, but not split and return)
• Could do some traditional HoT autobomber stuff with Storm Secret and Shock Nova + Astral Projector + Mjolner

Hope that this gives some ideas to play around with. I'd be interested in hearing about any other potential use cases for Hidden Blade.

EDIT: Follow-up post with videos