When they get to the rocky area, Talon will try to find the best paths from above (Perception d20: 16) and help crossing the more difficult bits by tying rope for the others to use. (Survival? d20: 16)

Son gets admiring his own bright red scales and how pretty they are compared to the grey stones, and only belatedly realizes that they weren't paying full attention to their surroundings.

Ember, attempting to bound from rock to rock, falls into a crevice, and is jammed. As she wiggles about, she slips deeper, and falls out into a hollow space, and taking 6 damage on the fall. It has an odd odor to it, and there are some bones in the corner, though no one appears to be home at the moment. She's able to be pulled up easily with rope.

Blue meditates a bit, and gets the sense that the forest itself is not hostile, it's just filled with hostile creatures.

Mark is able to navigate the stable rocks well, but isn't sure that they are heading in the right direction.

Talon isn't any better able to spot a good pathway from the air, the rocks don't betray much in the way of how to head.

 The gap in the rocks that you think leads to the pool looms up ahead, but behind you, towards the base of the rocky embankment you've been climbing, you hear a skittering sound, and there is movement across the stone. Small, elongated bodies with dozens of pairs of legs swarm over the rocks, heading in your direction, currently 60 feet away.

They are slower than your walking speed on flat ground, but don't seem to be impeded by climbing the boulders and rocky bits. You guys can turn and fight, or try to flee. If you opt to flee, it'll be over difficult terrain, and I'll have you give me an Athletics of Acrobatics check at the start of your turn to make sure you don't loose your footing (DC 10 or prone).

"Uh. You see those things? Do we run or should we try and fight?"

He looks over at the barely standing Mark.

He tries to gauge how long until the things reach them and then wonders what they could possibly be.

Perception?:14

Nature:16

If you stand your ground, you've got 12 seconds until the centipedes are on you!

((Any chance he would have gotten a count on how many there are :D?)

Big'un  will say: "Maybe we need to try and retreat. Those with ranged attacks can do so as we back up."

since at least the first one is within 60' Big'Un will cast ice knife at second level attack (no Mod): 14  for 1 piercing damage. then it and any others within 5' of it must make a Dex save of ? or take 8 additional cold damage.

he will then back up as much as he can....athletics check (no mod): 8

Edit to ask: how many do we see?

Feeling safe in the air, Talon will take shots to try to chase the creatures away, or at least weather them down.

Attack: 14 Damage: 6

Blue will stand his ground, morphing into an axe beak once again.

"I don't have much energy left for another fight. I fear I think we must flee." Ember says as she turns to try and find the best way to get away from the giant bug. 

Perception: 4 

Acrobatics: 1 

(no mods. I'm hoping dex is better than strength, but we will see)

(lol....nope! Ember is going to die trying to run away)

Son sees that Ember is trying to make a break for it, badly. He turns back to the critters and readies his dagger, just trying to remember what he could possibly do against a group of little beasts.

He stands next to the odd thing that was Blue.

Memory: 2

((Big Un, can you roll me a d20? I'll handle it from there.))

((There look to be hundreds of the thing...))

((Son, you have a Memory Die if you want to roll it!))

((Also, since you're at least partially engaging them, go ahead and give me initiative!))

((I did roll it. Is it not showing up? It was a 2.))

Initiative: 4

D20 roll: 18

initiative (no mod): 6 

.

.

Initiative: 20

(My last two rolls were a 19 and a 20.  Game’s not supposed to be this nice to me, but at least I get confirmation of my Dex mod.)

((Blue, your initiative is +2.))

Son is a bit distracted thinking about how awful it would be if you were sleeping and these things swarmed your bedroll. In a moment of clarity, you realize you know the alarm spell, and could ward your campsite so at least you'd know they were coming.

Initiative (no mod): 2 

((So very fitting with me trying to run away badly))

((Ha! Tell those centipedes to hold off 10 minutes so I can cast that spell.))

Talon's initiative: 6

"Everyone, get behind me.  Start moving away slowly."

Mark will sheathe his battle axe and grab one of his hand axes, ready to throw it if he needs to.

Initiative (No Mod): 15 

Blue turns into a bird, and is holding his ground.

Mark readies a hand axe to throw (and may do so now!))

The centipedes swarm up the rocks towards you, cutting the distance to ~25 feet!

Talon takes the the air, and fires a bold down from above that skitters off a rock as it shatters, taking out the centipedes nearest it.

Big Un blasts a spear of ice into one of the swarms, freezing a swath of them on the rocks, before clambering another 15 feet upwards.

Son stands shoulder to wing with Blue, dagger at the ready.

Ember turns to run, and falls down, scrambling back up, making it up near Big Un. 

((Blue, you're up, the centipedes are 20-25 feet away at the moment, Talon is in the air, Mark and Son are standing with you, while Big Un and Ember have moved up the hillside.))