Disclaimer: this is not a serious and/or min-maxed build, but I really enjoyed thinking about this concept, so I wanted to share it.

How it works

There are two main gem groups:

• (Cast on Crit) Lancing steel of spraying - Desecrate - Raise spectre of transience
• (Fire Mjölner) Detonate dead of chaining - Bodyswap of sacrifice

When lancing steel is used the following happens in an ideal scenario (in reality there will be CDR mismatches and missing procs, but overall it is somewhat smooth in the gameplay):

1. Projectile hits enemy with the crit
2. Cast on crit procs desecrate
3. Fire Mjölner procs DD, which starts cleaning up the non-spectral corpses from desecrate
4. Second projectile hits with the crit
5. Cast on crit procs raise spectre on a spectral corpse (spectral corpse is not guaranteed, so it can be any corpse in reality)
6. Third projectile hits
7. Fire Mjölner procs bodyswap of sacrifice on the spectre
8. Repeat

POB: https://pobb.in/rnuDPxaxQ4lX (DPS in pob is incorrect, because it considers shield charge to be a source for the Fire Mjölner proc, I have no idea how to fix it)

Gameplay: https://www.youtube.com/watch?v=3psSDWTp0Vw

Spectre bank

While 3.25 fixed abuse of the desecrate pool for DD, since we are actually creating spectres, we can still utilize it to “force” a better target for bodyswap. There are two spectre gems in this build - regular raise spectre and raise spectre of transience. With regular spectre gem we need to raise a single high HP mob from t17 maps (e.g. Disruptor), desecrate then will use corpses from this pool. Raise spectre of transience is then used in a Cast on Crit setup and it doesn’t alternate the desecrate pool.Additionally, since DD now can’t explode spectre/spectral corpses, the probability of Raise spectre targeting a high HP corpse is also higher.

Stationarity

While shooting lancing steel we don’t move at all, so you can just hold a button and everything will happen automatically. At any point in time the character is considered to be stationary, thus we can use things like Arctic armour or Ramako, Sun’s Light (I've also pobed Chief version, but it requires a lot of effort to solve mana problems).
Though, you can’t use Soul of Tukohama, because each cast of bodyswap will be considered as moving.

Conclusion

Is it a good build? Probably no, it is a real pain to try to pick something from the ground while your projectiles are still flying and can at any point in time teleport you into another location. Is it a good value for your buck? Also no, it requires a very expensive enchant on top of a double-influenced axe. But it is very fun and for me it is the poe 1 experience with overly complicated interactions, CDR breakdowns and a gazillion of projectiles when you can’t say what’s happening on the screen.