First, a magma drake, trying to use its tremorsense to give it an advantage in the middle of a firestorm. Unfortunately, I forgot about the concealment penalties for the PCs. It went down in fairly short order, particularly due to a combination of a barrage of magic missiles from Larissa (who had fire eyes from Liandra letting her see clearly) and an awesome turn of two critical hits from Turok. It bowed as it died, like the drakes of the previous days; I felt gratified by how much of an emotional reaction my players had to the enigmatic bow.
Then at last the brainburner that I'd been pondering for so long. (I've unlocked two of my posts about it here and here.)
I never did come up with a really attractive illusion the way I'd hoped. In a story, the illusion might have been a cool pool of water--but I think that I was right when I decided that my players would be instantly suspicious of that. So instead, I tried an illusion of an exotic ruby dragon-oid, looking naive and uncertain and vulnerable.
It did not work.
In fact, Turok noted how slowly it was moving, and decided to study it closely to see whether it was an illusion. He did--and he made his Will save and saw through the disguise. That in itself makes for a good story: when it counted, Turok was able to see through the illusion.
They were proposing to just walk away from the monster, but a) I didn't want to waste all this intensive monster design, and b) I had given it the roper's 10-foot movement rate, and it was just barely able to shuffle forward and fire a sticky strand at Turok, which hit and started to reel him in. I did at least a decent job of describing the overwhelming pattern of sights and sounds that had him fascinated, ignoring even the sensation of his mind searing.
Kyle ran up and almost severed the strand (only "almost" because I forgot about his damage bonus against magical beasts :-( ), but then got a strand attached to himself. He made a lot of his Will saves successfully, but had trouble capitalizing on them; he couldn't manage to sever his own strand and Turok's in a way that did much lasting good.
Liandra got in the first real damage with her bow. She also summoned an arrowhawk to zap it--unfortunately, it turned out to have electricity resistance 10. (Fortunately, it got at least two critical hits.)
Finally, the PCs realized a better strategy: instead of trying to break the strands as it continually exuded new ones, Kyle used one of his moments of clarity to try to rush in to the monster's vulnerable body, and Larissa and Liandra assumed strong forms and rolled in to attack its body, trusting to their high Will saves to keep them capable. This worked; they managed to knock it down in fairly short order. (One of the risks of luring critters in to your vulnerable body is that if they do recover their free will, they're near your vulnerable body.)
This whole encounter was plagued by horrible luck on both sides, but particularly excruciating bad luck for the PCs'. Larissa failed a lot of her caster level checks to get spells off; Turok could not buy a decent roll on his Will save for love or money, and Liandra rolled a 1 on her Will save at a most inopportune time. On the other hand, I was plagued by cruddy rolls myself--including one round where I rolled three 1's in a row when trying to hit Turok with a tentacle.
Turok took the most ability damage, getting down to Int 5 and Wis 2 before the brainburner was finally dispatched. I'm pretty happy with the slow 1d2 ability damage per failed save; I flatter myself that it felt more ominous and foreboding than the harsh 2d8 ability damage of the roper.
Next up: a fight with some of the creatures that fit the Gorge of Fire perfectly, but which I have so far left out. Plus, a pacing problem for me, as I try to decide what to do with the one short encounter before a natural transition that I'd hoped to fit in tonight.