Little extra context for this side passage, it looks like it was dug, and trapped, by kobolds. All of you will fit through without squeezing, but only one at a time. Given that it lets out by the barracks, that may prove problematic.
Just in the brief time you've observed, its varied a fair bit. They seem to move around a lot. But you can probably expect around 2-3 dozen. The trolls tend to stay separate from the others, probably much to the relief of the kobolds.
Gk, your not the only one that can unleash a devastating spell, in close quarters.
Mapping out the barracks, secretly would be the key here. Before, we unleash something nasty inside?
I'm sort of reminded, how soldiers attack an armored bunker, or tank here. How, they used a special mortar, and/or smoke grenades. To help penetrate, and flush out the enemy.
Maximum damage, to a large group of hostiles, in a confined space, plus with the element of supprise?
I like where your headed Gk, with this, I like it a lot.
Ok, how can we get the supprise, down this rabbit hole? Invisibility for sure, can you imagine, if the other entrance, was flooded, and this one corked up?
Narrowest part of the tunnel is the river entry, and that's an oval averaging 20' in diameter.
Unfortunately for the Wile.E.Coyote idea, the illusion is not visible at all from the inside and would not hide a wall that way. That was probably deliberate so that the dragon could safely observe at least part of the area around before exiting.
Edited: daishain on 4th Jun, 2018 - 5:45pm
So, by that basis, a Wall of Stone would put 5 layers of wall, approximately, to block most of the entrance? Again, leaving enough room for water to flow fairly unimpeded, even if it's just a couple of feet at the bottom of the Walls, anchored into the roof.
To the party - this only works if we stay for the 8 hours required to change spells. Otherwise, we go in now, as is, after taking down the familiar. We need to decide really soon, even though we are far from the lair and the hawk observer, just to prevent random events, etc.
Edited: Gknightbc on 4th Jun, 2018 - 10:23pm