Zippy takes a few steps into the boneyard. There’s is no sound except for the crunch of bones under the steeder’s feet. Jeth does not answer Valrish’s call, and the eeriness of the situation puts everyone on edge. All at once the sound of bones clattering and clacking erupts as 8 skeletons burst forth from the boneyard surrounding zippy. The steeder raises a single leg to Oorr.

(OOG Zippy, Oorr, Eldeth, Jmjar and Grimnir may act first due to stealth and perception. The Skeltons are closing in on zippy and are 10 to 20 feet in front of the rest of you.)

Oorr flies over Zippy's position, staying 15 feet from the ground. He shoots a bolt to the nearest skeleton, then commands Zippy to attack the same one.
Heavy Crossbow: Attack: 9 Damage: 12
Zippy Bite: Attack: 8 Damage: 12

OOC I left the poison die out of Zippy's attack since the skeletons are immune to it.

As the skeleton rise, Jimjar releases his arrows.
Shortbow: 15 damage piercing 6
Shortbow 2nd attack: 9 damage piercing 4

Still in the shadow, Grimnir run towards a skeleton and delivers a series of blows.
Mace: 13 damage bludg 7
Free hand: 17 damage bludg 7
After delivering his hits, Grimnir is retreating 25ft away from the skeleton (no AoO)

Initiative if needed:
Grimnir: 18
Jimjar: 17

EDIT: I didn't double the damage in this post, but if I recall correctly, skeleton are vulnerable to Bludg damage

edit2 forgot the sneak attack of jimjar. Add 2

Three skeletons shatter into pieces quickly to those of you who were watching carefully. Mace and fist burst through bone, and the pieces are lost in the boneyard. Some of the remaining skeletons close in on zippy with short swords while others shoot arrows at the attackers they can see.

Skeleton 1 SS on Zippy: Attack: 15 Damage: 8

Skeleton 2 SS on Zippy: 16 Damage: 8

Skeleton 3 SB on Oorr: 14 Damage: 3

Skeleton 4 SB on Grimnir: 14 Damage: 6

Skeleton 5 SB on Grimnir: 12 Damage: 3

I try a frostbite on one of the skeletons shooting at Grimnir.  6 cold damage on a failed DC 15 Con save. 

One arrow flies over the head of Grimnir. Another arrow is aiming for his head. In a quick second, Grimnir extant his hand and catch the arrow (8)
Using the arrow like a dart, Grimnir throws is back toward the skeleton (8 damage 6 (using 1 ki point)

Quote from Matthias_von_Schwarzwald >>

I try a frostbite on one of the skeletons shooting at Grimnir.  8 cold damage on a failed DC 15 Con save. 

 Con Save 8

Oorr Initiative 5

Ooc sorry on phone, I’ll do basic:

Jimjar will try to hide before releasing his arrows.

Hide 20
Shortbow: 22 damage piercing 4
Shortbow 2nd attack: 22 damage piercing 7

If sneak attack: add 2

 Grimnir run a second time towards a skeleton and delivers a series of blows.
Mace: 19 damage bludg 5
Free hand: 23 damage bludg 4

critic !!! Add 4

After delivering his hits, Grimnir is retreating 25ft away from the skeleton (no AoO)

Eldeth shoots two arrows at the Skeleton attacking Oorr, and then two more at one of the ones attacking Zippy:

Skeleton attacking Oorr:
Attack: 16 Damage: 5
Attack: 8 Damage: 8

Skeleton attacking Zippy:
Attack: 6 Damage: 4
Attack: 22 Damage: 6

Valrish runs up to the other one attacking Zippy, and proceeds to slash it twice with his Greataxe:
Attack: 9 Damage: 5
Attack: 14 Damage: 13

More arrows and fists fly, knocking down skeletons to the ground. Valrish gets his first taste of battle with a new weapon, and slams through a skeleton from behind in one cleave. Three more of the creatures are defeated, leaving just one attacking Zippy, and one more shooting arrows towards the group.

Skeleton 1 SS attack on Zippy: Attack: 18 Damage: 3
Skeleton 2 SB attack on Oorr: Attack: 14 Damage: 5

(OOG Open rolls, two skeletons left.)

Oorr drops the crossbow and takes the rapier. Both he and Zippy attack Skeleton 1 simultaneously.
Rapier: Attack: 22 Damage: 6
Zippy Bite: Attack: 9 Damage: 6

Quote from filcat >>

Oorr drops the crossbow and takes the rapier. Both he and Zippy attack Skeleton 1 simultaneously.
Rapier: Attack: 22 Damage: 10
Zippy Bite: Attack: 17 Damage: 10

 The skeleton shatters under the combined attack, leaving just one standing.

with only one skeleton left, jimjar and Grimnir unleash their attacks.

Shortbow: 15 damage piercing 6
Shortbow 2nd attack: 24 damage piercing 3

If sneak attack: add 2

 Grimnir run a second time towards a skeleton and delivers a series of blows.
Mace: 11 damage bludg 8
Free hand: 18 damage bludg 3

As before, After delivering his hits, Grimnir is retreating 25ft away from the skeleton (no AoO)

The last skeleton clatters to the ground, now indistinguishable from the other bones in the open cavern. The silence that follows is strange after the burst of activity a sound. As you gather your senses a soft voice, as if from a distance, calls out. Following it, you reach one of the edges of the boneyard where you discover Jeth lying on the ground. His body is shriveled, withered, as if the life was sucked out of it. When you approach his voice croaks, barely a whisper. "My men... they... they are gone.... we found a tomb, and she... asked for help... but we.... were not... prepared." He coughs, a dry and air filled cough, and his eyes roll back in his head. He lifts his arm to point at something, then collapses limply against the bones at the edge of the yard. Where his hands fall, you see the fingers pointing toward an opening in the cavern wall to the West.

Oorr checks if the duergar is still alive.
Medicine 9

Quote from filcat >>

Oorr checks if the duergar is still alive.
Medicine 19

Jeth shows no signs of life. After careful inspection, you do not find any wounds from blades, or bruises from blunt weapons. Instead it appears as if his body has been drained of fluids. His skin is flaking, and his arms and legs are shrunken in. You have to be careful when examining as any pressure seems it might turn him to dust.

"No sign of weapon wounds. It seems just... drained of fluids. Be alert."

Oorr will commune with nature once again to detect what kind of creature is nearby.

Primaeval Awareness (1st level spell slot): As an action, you can expend one ranger spell slot (1 minute per level of spell slot) to sense whether any aberrations, celestials, dragons, elementals, fey, fiends, or undead are present within 1 mile of you.

Quote from filcat>>

"No sign of weapon wounds. It seems just... drained of fluids. Be alert."

Oorr will commune with nature once again to detect what kind of creature is nearby.

The voice fades almost as quickly as it started, but you are left with an image of a tomb door and the path that leads to it from the tunnel. It is not far.

Everyone around Oorr sees him jumping by the surprise of having a voice in the head. After calming down, Oorr explains to the others: "This place is filled with undead. But there is something else. A creature of the Upper Planes, although I am not certain. It... spoke to me, it wants to be free. It showed me a path to a tomb nearby, it is in there."