Kadrick's Vault Plan
If the vaults are down low:
Entry: Holly casts Waterbreathing on the party.
Tie together against current, walk underwater to grate – probably helpful to bring climbing gear to help with grip.
If it’s cold water, endure elements to ignore.
Grate opening: Ognuts should be able to open a simple lock, or Ros do it – she’s rogue skills? Worst case, Mord bends bars/lifts grates :)
Silence cast on dagger to conceal sound of breaking in/breaking the boxes.
Vault lock: – similar to grate.
Box opening:
Presuming that the boxes are completely immune to magic (so no knock), and we don’t have ability to dispel that protection?
Locate Object to target the correct chests in priority of Plate, Mirror, bonus.
Windwall to blow away the miasma, so we don’t die working on the boxes.
OR: perform it from within a Rope Trick (better, but don’t think we have this)
Acid poured on hinges. Long prybar or gripping tools to allowing working at reach from behind windwall.
If wooden: warp wood.
acid flasks galore, or combine with Giant Bombardier Beetle to do acid damage 1/round, down an eavestrough type to channel the acid onto chest hinges. Periodically wash the channels to help them survive.
Mord big maul with long hafts.
If the miasma is just poison, neutralize poison on Mord, and he just rampages on the boxes.
Silently. :)
Transporting loots:
Pass without Trace so no tracks.
Phantom Steed for carry capacity and speed.
Plan2:
Stoneshape vault floor or walls, or soften them and we dig passage from vault to water, slide them right into the water.
Levitate on metal rods. Slide through brackets on boxes or slide the boxes directly onto the rods, use their magic to help lift.
Plan3:
If we cannot open the boxes no matter what, then we use magic to hide our travel up, find the big bossman, suggestion that he open the boxes to trap everyone in the mirror and gloat, and Mord holds off the hordes with whomever will help. We need that plate to reach to stop the armies to save the world.