The scorpion traps are one of the most useful things... you do need the traps skill for it, though. Select the skill, select the trap, and then right-click. Down in the orc encampments, I like to let loose about ten scorpions at a time, and just follow along to collect the goodies
There's another dungeon where they come in really handy as well... I forget which one.
I haven't cared much for the rest of the traps (spider mines and whatnot). They're not as helpful.
To get into the basement, you need the key. I think you do a favor for the merchant's guild, or you steal it some place.
As for charming, the number of charms you can place is dictated by your charm skill level. It sounds like you're at level 1... when you go up, you can add more.
Didja know the charm cheat?
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Open the item up multiple times, and you can put a charm into the first slot on each one of the times you've opened it up. Nice way to create an uber-powerful... weapon or whatever.