Recently, my players decided to rob the wealthiest noble family in a drow city. I didn’t see this coming, even though I should have. Of course I should have. It was money, dangled in front of PCs. What else would they have done?
Anyway, I’m running this drow city off the cuff. I have a map showing the strongholds of the noble families. I know the goals, styles and key members of these families. Everything else, I make up as needed. It’s a refreshing break from my habit of overpreparing. But it did mean that I needed an awesome security system on the fly. I mean, the drow don’t mess around. The wealthiest family’s treasure horde is going to be well-protected. Guards and pressure plates aren’t going to cut it. They need something awesome.
It also turns out that this wealthy family are talented psionists. This makes it clear what the defence should be: something that attacks the mind. A psionic dungeon.