Plant-creatures don't respond.

The vine-creature's route takes them gradually closer to the enormous wall of plant.  Eventually they arrive at - 

Well, it looks like a patch of enormous plant wall exactly like every other such patch.  But as they approach, vines and thorns and plates of bark shift aside, making a gap that expands into a gateway big enough to admit a truck.

The ground on the other side of the wall is startlingly more lush, covered in bright green grass and bushes.  There's a dirt road leading to a distant city, and a pair of building-shaped trees flank the entrance.

A couple of actual human people emerge from one tree, carrying what look like maces with tangles of living thorns for heads.  They approach.  The older one, who seems to be taking the lead, looks him up and down.

"You got here fast," he says.  "You okay, son?"

"Yeah, I am. You were warned I was coming?"

"Scout saw you, our technician got word through our Wellspring.  Come on through.  What were you doing out in the Wastes?"

"I'm from another world, I'm not whatever species probably human you are, I arrived there, a dragon thing attacked me, I killed it, then these plants brought me. My name is Sadde."

The man's eyebrows raise.  "Another world?  How d'you mean exactly?"

"You killed a dragon?" the younger man says.  "On your own?"

"This isn't the only universe there is, and I have a means of mostly undirected interdimensional transportation which led me here. I'm also a ridiculously overengineered species, very immortal, so yeah I killed a dragon on my own. ...well I punctured its brain on my own, that might perhaps not have been enough to kill it depending on how dragons work. It did stop moving."

"That probably did it," old man says.  He exhales heavily.  "Get all the blood off?  - That's important, you don't want any of it in the water."

"I used a magic thing to clean me of it and get me new clothes. What's it do?"

"Dragonblood grows tapewyrms, tapewyrms turn you into a chimera.  'Snot fun. It can corrupt a Wellspring too, but we don't know how much it takes.  - You have Wellsprings where you're from?"

"No Wellsprings, my world's magic is different. What's a chimera? Does that happen to nonhumans as well?"

"It'd happen to other animals if there were any left.  Think bugs are too small.  Chimeras're anything with a dragon head growing out of it.  Dragon head wants to kill everybody, just like ordinary dragons."

Young man asks: "If you don't have Wellsprings what do you do for immortality?"

"My species just is immortal. I'd expect the chimera thing to not work on me, also, both because of species and because of personal magic."

"Lucky you.  You need a place to stay?  Ride into town?"

"Not really, but thank you. I'd like to—understand what's going on better."

"Mm, I may not be the most qualified person to explain everything to you.  Plus we've got to get back to our posts, if you don't need anything else.  You could go into town - follow this road to get to Exaloc proper - and talk to one of the Sky Knights posted there - they're the folks who usually kill dragons.  They're shuffled around every so often so they know a lot about what's going on all over, 'n' they don't have much to do if there's not a dragon attacking."

"Okay. Is anyone going to be extremely alarmed if I run just shy of at the speed of sound?"

"I imagine they'll think you're an odd sort of Sky Knight, not a dragon or anything - they'll be startled but they won't set the watch on you."

"Okay. Thank you."

And he doesn't break the speed of sound because causing sonic booms is rude but he comes close.

Nyoom.  He reaches Exaloc in a few moments.

The city is made of trees: trunks thick enough for a spiral staircase support interconnected globes of weaved and melded branches, windows open to the air or shaded with clusters of leaves.  Dirt and cobblestone roads weave between the trunks, thronged with people and heavy-duty plant creatures, squat pitcher plants carrying shaded passengers and lumbering root vegetables hauling goods packed into gourd-carriages.  There's no division between road and sidewalk; no one seems worried about being run down by a large plant.  The roads are pleasantly shaded, by the higher-level tree-bridges and above them by a canopy of leaves.  The air is filled with the gentle murmur of a busy city with nary an internal combustion engine.

And is there anyone around whom he might be tempted to call a "Sky Knight"?

Well, not on the ground, certainly.

Most of these tree trunks have doorways; there are, indeed, spiral staircases inside of them.  Some of the big suspended buildings are bigger than others.

Here's a pretty big one, made of the interleaved branches of at least eight different trees.  It's hard to tell from the ground but it looks like it might be open to the air.

Then into that one he goes.

The staircase he takes is labeled "watch-house," and it leads to a balcony surrounding a - well, it's some sort of building, certainly.  These tree branch amalgamations can be hard to tell apart.  There's a leafy curtain set into one wall, probably an entrance.  No windows, but there's bushes on the roof that might be protecting skylights.

And it is very likely he can both hear and smell people so if he follows that...

It sounds and smells like there's people inside, certainly.  Past the curtain is a perhaps-receptionist at a perhaps-receptionist's-desk who looks up when he enters and says, "Hello, can I help you?"