This sounds like it could have been Tsu the Diviner who made this pact. But then again, we just don't know that many people of antiquity who would have walked these lands, so it really could have been nearly any powerful traveler who wanted the thing imprisoned in ice to remain imprisoned.
Seeing how surprised the beavers were at the "Forest people" and "Horned men", I really doubt that they made the deal with Tsu or even the Weilu in general. Most likely they were the ice mountain tribes, like the one that got married with the Meng/Diao ancestor, before they retreated further south.
That dark, dead thing being imprisoned inside a glacier just strenghten that theory. Should we bring this up with the White Sky envoys next month at the summit place? They could have actual records, or at least legends, about what we are dealing with. Or is it too confidential?
If there's a greater intellect behind them, it's going to be more wary if there's forces that can actually fight back operating in support of the Falling Waters Palace. Probably won't send individual raiders anymore, which'll mean it'll take time between assaults but be heavier in turn.
This is likely the only time we'll be dealing with only a single one.
Ling Qi frowned, eyeing the glint in the sky that had taken off from the top of the distant glacier, they had a minute or two at most, especially if they were to move to avoid damaging the dam. If the beast was right trying to hold it might be very difficult."
My take is that the galcier body has been infested by these star and/or void demons, burrowing in to try liberate whatever is inside. Then some of them go out to keep the beavers at bay and without interfering. If they are wearing down the glacier, they probably can't spare to send too many away or they will risk being pushed back. If there is a commanding one among them, it could still be possible to ambush scouts and the like.
Now, regarding the vote. Most of my concerns have already been taken into account. The collateral damage is a decisive factor, we did come here to stablish friendly rapport, and the sect is already partially responsible for the damage caused to the beaver's court. Let's not forfeit that at the first shinie, though lore shines are really alluring, that comes along.
[X] Allow Gan Guangli to play the bait, while you play the deadly wraith, trapping and killing it once it engages him. (70% success. Beast slain, low risks of collateral damage. Less intelligence on similar creatures.)
[ ] Take point yourself soaring up to meet in in the sky. Trapping its attentions in your mist and illusions, give Gan Guangli the time to set up his technique. (50% success. Beast captured or slain depending on degree of success. Higher risk of damage. More intelligence on similar creatures)
What really bothers me in this choice is that even "success" doesn't guarantee
actual success. If we roll just above target, the beast will be slain anyway. So we wouldn't get much more intelligence anyway, only the higher collateral damage from the creature's trashing.
We know that there is a whole infestation of them up in the glacier that we have to deal with (this site has completely overtaken the Cathedral in my priority list). So we can come back as soon as possible with proper formations traps and such, instead of doing a rush job.
Heists require proper planning and preparation, specially if we are heisting an outside-world demon from a glacier prision.