I had a few ideas for some additional curses, or weaknesses. They are not undead related, and I realize that stuff like this is unlikely to make it into the current dev-cycle. I'm posting it anyhow, since I'm likely to forget about it otherwise. They're similar in nature to vulnerability to daylight in that they force the player to change his or her behaviour.
Slave to nature: Being afflicted by this curse or weakness, makes you strongly dependent on nature; you are bound to its area of influence. More specifically, you can only walk over tiles with natural vegetation on them, if you're not connected to nature you will suffer. walking on constructed roads, bare rock or soil, or other trespassing would give a (randomly generated?) penalty, for example activation of a nasty syndrome, excruciating pain, petrification etc. It should be associated with (randomly generated) positive traits; druids, creatures like nymphs, and elven mages could suffer from this.
Enemy of nature: The opposite effect; When afflicted by this curse or weakness, you can NOT pass over tiles with natural vegetation on them, (grass. moss, fungus etc). Travelling from city to city, for example can only be done over the road. You would have extra reasons to hate the elves.
There's some fun in character tactics to circumvent not being able to navigate natural areas this way, like burning them to the ground so you can pass.
Anyhow both are likely to be career changing curses, and would limit your ability to explore, the negative effect should not be instantly fatal, it should likely be more subtle. You could visit these areas, but you would be very uncomfortable there. It would force you to play the game differently, which can be refreshing every now and then. Also characters affected by one of these should probably be unable to wear shoes or socks, as that would stop them from being able to connect to nature/rock. (Or maybe they could wear shoes with the soles cut out or something). Both ideas probably need some more work, so feedback is apreciated.