Next version, any dwarf that starts to alternately display a plumphelmet symbol or have tendrils of fungus emerging from his/her beard after visiting the underland caverns, will be locked outside -or better yet- incinerated in magma!
This sounds like too tempting a surprise feature for Toady to pass up.
I do hope so! We really only need two tokens. (one of which we might already be getting). First, we need the ability for syndromes to alter behavior. It appears we'll at least be able to make creatures to berserk/aggressive. Perhaps it will be low-hanging fruit to also be able to have them go melancholy or into gibbering insanity. That lets us add insanity syndromes to heavy metals, too
And then, obviously, we need the "give birth to nightmare inducing abomination" token as suggested by darkflagrance
A syndrome token that causes the infected creature to give birth to a specified race would be super cool for more than just this one thing. Xenomorphs from the Alien movies, for example. Bonus points if it allows for the specification of a different caste distribution than the default for the target race. So that you could have a race with a few casts, but one of them has 0 probability of being born. But the ones that can be born can infect other creatures, and those creatures give birth to the third caste. That would need a lot of work to function in world-gen, though. Or perhaps not, since night creatures already do something similar in world-gen.
Along those lines, a curse that causes a person to give birth to assorted random monsters (forgotten beast generator style) is a very mythological sort of curse to be meted out by vengeful gods. (OK, I think the Greek monsters like Hydra, the Nemean Lion etc were birthed by a titan, not a mortal woman, but still!) It may even be a way to keep a world's forgotten beast/titan populations up, rather than allowing forgotten beasts to reproduce directly, which has been suggested. An epic-level quest might be to find and kill a women cursed by the gods to give birth to monsters for all eternity. Sounds easy until you remember that she'll be surrounded by a menagerie of forgotten beasts!