(((Spoiler))))
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If you have not done Chapter 1, please don't read further, as it may spoil the experiance for you.
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Helms Hold Issue:

When I get into the basement of helms hold and when I free the last living Helmite from his cell, there is treasure & are zombies galore for fun. Assuming the character survives and loots that 'L' shaped room surrounded by cells, the last cell (the toe of the boot of the 'L')is closed and has a trapped chest inside. I have kept every key the game allowed me to keep, have a master thief with me that can't pick it, have cast 'knock' to beat the band, and it still won't open.

I have even gone so far as to import Godly characters to bash it with weapons that should have sheared off a quarter of the planet's crust with a single hit and left only a scarred wasteland of the rest, with only a handful of mutant survivors left to wail and lament my wrath. Battle damage is listed in scientific notation to save space, yet I'm told "your weapon's ineffective".

Q1: How does one open that chest?

Q2: What the heck is inside of it anyways?

I had it opened by Tomi Undergallows (it has DC 34).
It contains a powerful random item (not so powerful compared to what you can get late in the game but powerful compared to what you get in chapter 1).

This chest has been the subject of many other posts. The consensus is that this chest is protected against any physical attacks. You need a rogue to pick the lock. If you are not a rogue yourself then take Tomi with you. I heard the pixie familiar can open the chest as well.