When I start to master the FSC, I want to begin to make some shadow lair sets. What I'm thinking of so far is:
Shadow Gloaming Wild Woods
Helm: Deadshot Chapeau (some shadow defense, and a damage bonus against undead)
Armor: Deadly Virulisk (piercing and poison defense)
Shield: Dread Skelly Shield or Crest of Almire if I'm lazy (I'm assuming I'll probably only need to be really worried about howitzer bullets, so the shadow defense should be nice)
I'm not too worried about weapons; I think a Polaris, BTB, DA, and Shivermist Buster should be fine.
Shadow Royal Jelly Palace
Armor and helm: Skolver, duh.
Shield. Maybe a BTS or an Ironmight Plate Shield (for piercing, and either a damage bonus or a ton of normal)
Well, an AoA or Combuster might be nice. I'm not so sure about a FoV, as I wouldn't have any fire resist to protect me from the charge attack.
Shadow Ironclaw (or Darkfang?) Munitions Factory
Helm: Mercurial Helm (for shock, and the MSI might help a LITTLE. plus it looks awesome)
Armor: Vog Cub Coat (for elemental, fire, and sword ASI)
Shield: Grey Owlite Shield (for elemental, fire and shock)
I'm not really sure about weapons, except I know not to bring any fire or shock weapons. Or alchemers. And maybe a Glacius over a DA because it is faster and might let me shield quicker to be safe from traps and rockets.
Shadow Firestorm Citadel
Helm: Deadshot Chapeau (shadow, curse, and bonus against undead)
Armor: Vog Cub Coat (fire and sword ASI)
Shield: Crest of Almire (fire and shadow)
For weapons, probably a BTB, a Polaris, a Shivermist Buster and a DA.
Sound good?
I can't comment on the rest, but your Shadow GWW setup sounds good: normal, piercing, shadow, and poison armor. Elemental and piercing weapons. Crowd control.
Just a note, because this wasn't clear to me at first: The Unknown Passage, which comes after the boss fight, is totally different; it has nothing to do with poison or beasts. For UP, you want various protections, various weapons, and crowd control again. Fortunately, you can change your equipment between GWW and UP (and in fact at any time during the latter).