Okay, here's our dilemma:
1) Imogen (when her bow is strung) can fire arrows 600 feet with no penalties. Only Total Cover will stop her (Good).
2) The gargoyles can dash-fly 120 feet in a round, and Ukee's captor ended round five 215 feet away from Imogen (Bad).
3) The gargoyle with Ukee is at 4/57 HP. A single shot from her ought to do it (Good).
4) The two gargoyles are only 55 feet apart, and they look nearly the same. Worse, they flew into the mists over the river, and are low enough to nearly always have total cover as they fly away. They're flying like that on purpose, with practice. (Bad)
5) I don't like telling my players "no, it's impossible". So there ought to be a way to pull this off. (Good).
6) Even if Imogen shoots the right one down, there's a strong chance that Ukee won't survive the fall (between the height, the potential to drown if she falls in the water, and the 500lb dead stone creature possibly landing on her (bad).
I thought it might be a good time to try out 5e's "Chase" mechanics, but reading them over, I'm not too fond of them. (Frankly, I can see what they're going for, but I can't figure out quite how to do it well.)
Maybe just one of my 3-skill challenges?
Goal: Rescue Ukee. Primary Skills: Perception (keep sight of them between the ruins); Athletics (run like hell - I'd accept constitution saves as well); Investigation/Insight (where are they going? Why?); Others (something you come up with). Finally, I guess we'd need Imogen to take the shot.
What do you think?