It does.  It hits the ground and scrabbles a bit, gets itself turned around, and starts bounding after him.  Rapid pulses of echolocation, followed by more bursts of LOUD.

Ugh.

Whatever.

He turns right around and runs towards the dragon at full speed, aiming for a collision.

It startles a bit, and its head goes for a lunge, sideways and feral like an enormous wild dog.

So he jumps, aiming to headbutt it.

He manages to slam into its forehead.  It yowls and starts trying to shake him off.

He doesn't particularly mind killing animals. How hard is it to break its neck?

Well, he'd be hard pressed to get his arms more than a third of the way around it, if he managed to climb over its forehead.  This thing is huge.

Yes and he's a vampire it's not like he needs to strangle it to break it. Does it have a spine he can punch or puncture?

Spine: located.  This thing's skin feels tougher than a similarly-sized mundane mammal's probably would, though.  He may have trouble doing much damage with just one punch.

Once he's on its neck it starts raking at him, with claws on the end of its wings.

He's a vampire with biokinesis, it should just quit already.

It won't, though, won't it.

Punch punch punch he makes himself physically stronger and more resistant punch.

Crack.  Scream.

It rolls over and starts slamming its own head and neck into the ground, trying to crush Sadde between them.

Good luck to it, he'll continue doing that until it's dead.

Once it figures out that it's not going to be able to dislodge him, it sinks its claws into its own neck and rips out the flesh he's clinging to instead.

Its blood smells rancid, like someone left a vat of the least palatable animal blood imaginable out in the sun and it somehow began to rot instead of just drying up.  It tosses the chunk of flesh and its passenger aside, and then there's another screech of sustained LOUD.

He turns his sense of smell off, lands neatly on the ground, and just looks at the dragon unimpressedly.

It pounces on him and pins him under its claws.  The screech flattens into a pure tone, like a pristine tuning fork held against his eardrum; its pitch tanks to the bottom of his range and below, and then begins steadily ascending.

So it doesn't want to give up. Fine. He deafens himself, makes himself even hardier and sturdier and stronger (and he has no idea how to make himself faster without messing with his synapses and really doesn't want to, he'll rely on the other things), detaches his own arms and regrows them, replacing his forearms and hands with five-foot-long vampire bone spikes that become literally as pointy and sharp as he can possibly make them (and that's a lot).

How does dragon feel about a vampire jumping with these spikes directly at its head faster than the speed of sound?

Well, that doesn't seem like a happy sound it just made.

It screams and squeals and retches, its neck thrashes with Sadde still embedded inside its skull, and then it collapses.

It's probably dead.

Hopefully the task of getting out from inside its jaws will be comparably trivial.

It is.

And he's slimy. Ugh. He rearranges his body back to its more usual shape, reaches inside his bag of holding for a piece of rose quartz, and wishes himself clean and clothed. There, that's better.

So—weird plant-wards?

It's a long walk, even for a vampire.  He won't get tired, obviously, but if he has to walk all that way he might get debilitatingly bored.  Unfortunately there doesn't seem to be much else around.

As he comes closer it becomes clear that whatever this thing is and whatever it's doing there, it's more like a single oversized plant - many times larger than a city - than a forest.  Thick tangled thorny vines and layers of bark and bulbous protrusions a bit like pitcher plants.

Walk.

Walk.

Walk.

Walk.

Fuck walking he'll run.

Run.

Run.

Run.

Yeah this is faster though.  This thing is huge.

There's plant-creatures moving around just outside it.

Are they plant dragons. Is that what his life is right now.

They don't have wings!  They're smaller!  The horrible stench of dragon blood is weaker as you get closer to the giant plant thing, as Sadde will notice if he's turned his nose back on!  Maybe they're something else.  Or maybe they're just small flightless plant dragons.

...do they attack him if he gets close.

One of them - something slender and four-legged with a tangle of vines for a body - spots him and sprints off.  A few heavier-duty ones approach, cautiously.