Eh, this post got away from me slightly.
Dhar is only bad if the waystones can't just suck it down and pump it out into the void.
Just wanted to note that we have confirmation that it is indeed so:
[...] a bloom of Dhar forms and begins to spread, slowly but interminably. You expel the Ulgu and activate the protections of the Room of Calamity, and the curdling Winds are drawn out of the room and flushed into the air.
There's no danger in that, you remind yourself. You looked into it when you first built the room. At this height it will be blown away, and if it blows west or east or south it will be one more drop in the oceans of the Badlands or the Dark Lands or Nehekhara, and if it blows north it will be drawn into the Waystone network and be dealt with by the ancient artifice of the Elves. When you learned that the Karak itself is eight enormous Waystones it simplified it even further. Within the hour it will have been captured by one of them and will be on its way to Karaz-a-Karak, where some ancient Runic masterpiece will somehow break it into usable and benign energy.
So in a suitable environment we can use multiwind manipulation enabled by Dhar-glue as safe as usual wind casting, because we are not manipulating Dhar itself, just using effects of its presence to manipulate other winds, so no adverse mental effects associated with mindset required to manipulate Dhar.
Or at least it seems like it, so why not spend an AP on researching it to confirm or reject it? If it would work and would not be too dangerous, it would be very useful.
There were arguments that it's not worth it, but I don't think they are convincing; let's compare with the reading of Liber Mortis.
First point, by Mathilde's understanding, investigation of Dhar-glue multiwind casting would be breach of Articles, and if she would willingly do it, her mental well-being would decrease because of the damage to her identity and feeling that she might be betraying some of her ideals.
It was the same with Liber Mortis, the difference was just a matter of degree. Mathilde herself states that reading Liber Mortis is not a breach of the Articles only on technicalities, and, implicitly, only based on her understanding:
One might be able to make an argument that simply reading the Book didn't count as 'study' under Article 7, but such was the reputation of the book that if anyone ever found out about it, no amount of technicalities could protect you.
And of course it was mentally straining for her, but with suitable preparation it was ok:
You are well aware of the weakpoints of the human mind, so even though there's no magical traps you take precautions against the more mundane kind. A roaring fire, a comfortable chair, Wolf curled up at your feet dreaming puppy dreams, a glass of brandy - insulation for the soul. You wait for your hands to stop shaking, and then you turn past the title page you first saw on the outskirts of a battlefield in Sylvania.
With keeping it secret and understanding that reading the book was worth it because of insights, knowledge, and abilities it granted, Mathilde was alright.
Second point, that it would not give us enough actionable benefits, that we could not use it and could not teach it because if we reveal it, we would be killed. Well, it's exactly the same as with Liber Mortis, we could not ever reveal that we had read it, but:
At the very least the insights it contained could be a powerful tool against the undead and possibly even the Skaven, but it could also contain deeper secrets on the nature of magic itself.
It gives us insights and knowledge on how things work, and just as knowledge from Liber Mortis was useful, knowledge gained from studying Dhar-glue multiwind casting would be useful. And just as abilities we acquired from Liber Mortis (e.g. second secret, forget about necromancy) is another tool we can use in a hypothetical extremely dire situation, it is possible that we would get comparably useful and not too dangerous abilities from the study of Dhar-glue multiwind casting.
So overall for investigation of Dhar-glue multiwind casting it seems that the risk is slightly higher, and reward
maybe is slightly lower compared to reading Liber Mortis, but it's still worth testing. If it would be revealed as too dangerous, Mathilde would not use it; otherwise, great! new applicable techniques and abilities! And doesn't matter if some of them must be kept secret, Mathilde's on her own in plenty of situations. And it both cases it would give us new knowledge and insights, which would be very good.
