Do they do anything at all in Dwilight? Would be cool if they did. If not I guess I'll just get rid of them.
Oh they do plenty... You like raining cows and pigs? I saw that happeen once on dwilight.
I used a set once and had nothing happen as a result. :'( Haven't been able to find any since.
I used them a couple of times when they were shutting down the Western half to wipe out monster populations so people could make it to port cities.
When eight portal stones are set in a circle, it sets off a beam/column of light into the sky and an annoying humming/buzzing sound until Further GM Response by Anaris or I.
The adventurer setting the portal stones is strongly encouraged to roleplay the setting of the portal stones, your motivation for doing so, the scen etc. Or as a witness, your reaction to seeing light column and hearing weird sounds. We use those, whatever local flavour exists in region descriptions, estate names, recruitment centers, unit names, local temples, local history, and imagination to create the event. You should expect unpredictability with portal stones in regard to your motivation, but the more we can play off of what the player is doing instead of spinning something out of thin air, the better. I have been trying to involve religion in more portal events recently as well, in an 'appeal to the divine' sense. That sometimes backfires with being connected to a less benevolent divinity, such as daimons.
Also, the strength and nature of the events differ by continent. Generally, BT will get the most unusual, magical events. Lesser so, Dwilight. Colonies less than Dwilight. EC with the least unusual/magic events, more along the lines of mundane disturbances that could be explained within a medieval milieu of superstition.
And to take it back to recommending more roleplay in-general - in all our busy schedules, taking time to write 2-5 sentences with an amusing twist on some regular BM event/text, can be a lot more effective than a long narrative. Some of my most fond BM memories are funny interpretations of everyday events, more than any Drama or Epic.