This whole "four horsemen" thing does sound very interesting. I still like the idea of the material you would otherwise get straight from the colums actually being from the tissues in the demons produced by the spire. Perhaps there is a way to be more subtle about this, though. Have the first person infected hang around for a while with the interaction infecting other people, then at some (preferably as unpredictable as possible) point after you mined the first piece of the spire, everybody who got infected turns at once and all hell breaks loose. That sounds to me like some serious high-level !!FUN!!
Entirely possible.
Draft of what's needed all in all:
Digging the special stone causes a burst of gas causing syndrome 0
Syndrome 0: 5% prob of able to do interaction 0 starting at 0 phases, 10% able to do interaction 0 at 100 phases, etc... ending at 2100 phases
Interaction 0: add supernatural to self and all others for 2100 phases, target cannot have supernatural, add to self syndrome 1
Syndrome 1: adds a recognizable set of tokens, can do interaction 1 starting at 1200 phases, can do interaction 2 starting at 0 phases, can do interaction 2 starting at 12000 phases
Interaction 1: spread syndrome 1 (free action, touch, delay 3600 phases)
Interaction 2: spread syndrome 2 (self only), target requires: mischievous
Syndrome 2: body transformation into <DEMON>
Interaction 2: targets all affected by syndrome 1 (identified by tokens) anywhere on the map, adds mischievous
Result:
* Unless you're very unlucky (.25% chance for >1) only one person is infected regardless of how many are affected by burst of gas; the initial infection time varies by 2100 phases based on luck
* After 1 day and then every 3 days, any infected creature infects another creature (leading to, optimally, something like 10+3+2+2+2+1+1+1+1=23 infected total during countdown)
* After 10 days, all infected transform immediately into demons
Since I already have lots of syndrome and interaction related raws, those being my modding focus before this, making the above framework would take me barely any time at all I should think. Just need the material and creatures.