The tents looked like normal cloth, so it wouldn't be that hard to cut through them. It might take a little bit, but it's possible.
Starting a fire that deep in from the outside... not so much. The map isn't to scale; it's more of a general idea, so that's out of range of your Thunder or Elthunder spell. You'd also have to carefully aim for something that would catch fire easily, which means you'd have to clearly see it.
If you were to be flying above the camp, you'd be able to do it, but you'd have to duck down into bow range. EDIT: Or you could set a fire somewhere on the outskirts of the camp from outside.
Hm. So we'd need a different plan in order to avoid telling the entire camp that we're attacking them and hence getting attacked by dozens of mercenaries at the same time.
I do still think that, all else aside, telling dozens of mercenaries to attack us is a pretty bad idea. So...two ideas.
[X] Plan Solid Drake
-[X] Primary Objectives:
--[X] Use magic lightning to set the outermost ??? tent on fire from beyond the edge of camp, hopefully without being seen. (Also hopefully, the wyvern tent will get caught in the fire.)
--[X] Sneak into camp once everyone starts rushing to put out the fire. (It's a fire in an important tent, lots of people are going to run and help so other people don't get hurt. Right?) Specifically, Robin and Ryza both sneak from what I assume is the northwest corner to Lady Sypha's tent.
--[X] Robin and Ryza use knives to cut a person-sized hole in the tent we're pretty sure has Sypha in it. (What
else could it have? Where else could she
be?) Rescue Sypha and run to the horses' pen.
--[X] If discovered on the way to the pen (which won't happen, we're all stealthy, right?), Ryza turns into a dragon and carries Robin and Sypha out of the camp ASAP—secrecy can wait until we're safe!
--[X] Otherwise, cut the horses loose, open the gates or knock down the fences, and steal a few horses to ride away from camp. (We can do this.)
-[X] Secondary Objectives:
--[X] Try not to fight anyone. We probably can't win.
--[X] If we come across Artemis's bow or Jack and can free/de-steal them without much risk, do so.
--[X] If we come across anything outside the implied parameters of this plan—like Jack in a place where we
might be able to free him, or something that might reveal the Talons' secrets, or Kelton being here for some reason—take a moment to think and figure about whether to chase that new thing or follow the old plan or what.
TL;DR: Basically the same plan, but targeting a probably-important tent whose contents are more mysterious. Hopefully it's not their powder magazine.
[X] Plan Solid Drake
-[X] Primary Objectives:
--[X] Use magic lightning to set the horse area on fire from beyond the edge of camp, hopefully without being seen. (The horses will just run, they'll be fine.)
--[X] Sneak into camp once everyone starts rushing to put out the fire. (It's a fire in the horse area, lots of people are going to run and help so the horses don't run off.) Specifically, Robin and Ryza both sneak from what I assume is the west side to Lady Sypha's tent.
--[X] Robin and Ryza use knives to cut a person-sized hole in the tent we're pretty sure has Sypha in it. (What
else could it have? Where else could she
be?) Rescue Sypha and run out of camp.
--[X] If discovered after rescuing Sypha (which won't happen, we're all stealthy, right?), Ryza turns into a dragon and carries Robin and Sypha out of the camp ASAP—secrecy can wait until we're safe!
--[X] Otherwise, find somewhere in the woods to catch our breaths and plan our return to Agrithe. (We can do this.)
-[X] Secondary Objectives:
--[X] Try not to fight anyone. We probably can't win.
--[X] If we come across Artemis's bow or Jack and can free/de-steal them without much risk, do so.
--[X] If we come across anything outside the implied parameters of this plan—like Jack in a place where we
might be able to free him, or something that might reveal the Talons' secrets, or Kelton being here for some reason—take a moment to think and figure about whether to chase that new thing or follow the old plan or what.
TL;DR: Set the horse pen on fire. We can't ride off into the...um...starset, but that side of camp is probably less guarded, and it's one less thing we need to do while in the camp.