Barty's "Lost Mine of Phandelver"

DM Screen:

Rows and rows of jagged spikes erupt from the ground as Finna weaves her spell. The mindless zombies plod right into it, taking 5 and 4 piercing damage, and stumble to a halt. The flameskull, however, is not hampered by the ground, and hovers over the zombies. Its mouth opens, unleashing an otherworldly scream, and three glowing darts fly from its jaw, all striking Nemean and dealing 9 force damage, causing his shot to fly wide.

Round 3 Order:
Players <=====
Enemies

Placement:
Two zombies are 10 feet away from the front line, in the midst of the spike growth.
The flameskull is 10 feet in the air and 10 feet away from the front line.

Tracking:
Nemean is lightly wounded.

The flameskull is lightly wounded.
Two zombies are lightly wounded.

Nemean has used 7 arrows.

OOC: Assuming Roland and Thulgrim are the frontline, since they are holding attacks for when the zombies come into range.

Roland darts out from behind a pillar and attacks the closest zombie with his rapier, thrusting with a savage fervor.

Attack: 14 Damage: 11

OOC: OK, so I'm wondering what's involved in making a mid-air attack against the flameskull ... Thulgrim can normally jump 9' as a standing jump (half his Strength) but with the Boots that triples to 27' which is still within his movement speed of 30' (also from Boots). So from a standing jump he could clear the spiky area. The maximum height of the jump is a quarter of the distance, so that's 6'9" which should be enough to stay clear of the zombies with them in the middle, but happy to make an Athletics check (PHB suggets DC 10). So Thulgrim should be able to strike at the flameskull. The skull has no melee attacks, so there wouldn't be an opportunity attack. How does that all sound?

Also, if I declare Rage with Frenzy Attack as BA on this turn, and try this maneuver on the next turn, can I make a second attack as my BA on the next turn (i.e. attack the skull TWICE while in the air?) RAW don't prevent any of this, but happy to accept any interpretation.

If all okay, see below. If I need to modify my action you can apply the roll to something else.

BONUS ACTION: Rage (just normal Rage for now pending decision)
MOVE: As described above
ACTION: Reckless Attack: Greataxe v Flameskull. Attack: 25 Damage: 12 +2 dmg from Rage

Athletics if required (with adv from Rage): 21

OOC: Oh yeah, forgot my off-hand weapon and sneak attack assuming I was hidden.

Attack: 8 Damage: 10

Sneak Attack: 9

Finna considered for a moment using the last drops of magic she had, but it looked like magic had might have better use. She tried to shoot the skull instead:

Crossbow Attack: 13 Damage: 10

Nemean takes another arrow from his quiver and points it directly at the flaming skull. He hisses as the flies towards his foe.

Longbow Attack: 11 Damage: 12

 (By the way Zorg, great job finding an image to convey what Thulgrim looks like as he performs his high flying attacks!)

OOC: Sorry for the delay, DMed for one of my RL groups today. Should have a post up in the morning.

OOC: Thulgrim can easily clear that jump with his boots, but the ceiling here is low (10 feet), so I'll use the Athletics check. What an absolutely brutal strike!

DM Screen:

Zombie CON Save: 17
Zombie CON Save: 5
Zombie CON Save: 14

Roland rushes to the zombies slowed by the spikes, skewering once, then again, tearing holes into its rotted flesh in its chest and throat. The stubborn creature clings to undeath, its groans becoming gurgles through its damaged windpipe. Above the rogue, Thulgrim leaps, higher than any dwarf should be able to manage, passing beneath the ceiling but above the zombies and landing just past the spikes, slamming his axe sidelong into the flameskull along the way. The skull cracks, losing a piece of its jaw as it is blasted into the tunnel wall. Finna and Nemean loose their missiles past the skull, missing the tiny creature by inches.

Strangely, the undead creatures barely respond to the brutal attacks. The zombies turn, walking right back through the spikes and taking another 6 and 4 piercing damage. This proves too much for the zombie attacked by Roland, and it falls to its knees before its face plummets, taking a spike through its brain. The flameskull as well responds to Thulgrim's beating by simply floating back toward the bellows in the room beyond.

Slam vs. Thulgrim: 10 Damage: 3.5
Slam vs. Thulgrim: 5

While one of the zombies stumbles right past Thulgrim, back toward the bellows, two more step into the tunnel, blocking his passage. The dwarf all but ignores the fist that lands on his back from one as he avoids the second.

Round 4 Order:
Players <=====
Enemies

Placement:
Two zombies are engaged in melee combat with Thulgrim at the entrance to the room.
The flameskull is 10 feet in the air and 40 feet away from Thulgrim.
The remaining five zombies are spread throughout the room with the bellows.
Roland is behind the spike growth and Thulgrim, with Finna and Nemean further behind.

Tracking:
Nemean is lightly wounded.
Thulgrim is lightly wounded.

One zombie within the bellows room is badly wounded.
The flameskull is wounded.

Nemean has used 8 arrows.
Finna has used 1 bolt.

Roland attempts to spring onto a nearby wall and use it to launch himself over the spike growth so that he can fight alongside Thulgrim.

Acrobatics: 18

Finna uses another bolt - her target is Skull and skull alone! Attack: 16 Damage: 5

Thulgrim has his steam up now, and he lashes out furiously at the zombies beside him, but looking with a wild eye at the skull floating away.

Greataxe Attack v Zombie: 23 Damage: 9

OOC: Assuming some success, Roland will attack the zombie Thulgrim is attacking and/or any surrounding zombies after that. If his acrobatic stunt has failed, feel free to ignore.

Attack: 24 Damage: 5

Bonus Attack: 19 Damage: 1

Sneak Attack: 6

Nemean takes another arrow from his quiver and let’s it fly at the flaming skull. Without moving his body he smoothly grabs another arrow and fires it off before the first can even reach its target. 

Longbow Attack: 20 Damage: 6

(Action Surge: Extra Attack) Longbow Attack: 19 Damage: 6

He then stowes his longbow in anticipation of charging into the next room.

DM Screen:

Using a single leap off the wall, Roland joins Thulgrim at the front line. Together, the two hack and slash the zombies next to them, but before they can land a fatal blow, the undead creatures repeat the behavior of those before them. They, along with the rest of the zombies, turn away as if nothing had happened, and walk back toward the center of the room.

A hail of missiles chases the flameskull. Both of Nemean's miss their target, but Finna's lands, plinking off of the skull and barely bothering it. The flameskull floats up and over the bellows, and disappears beyond - along with its soft green glow.

The zombies now simply mill about the room beyond this tunnel.

OOC: Updated ammunition.

Thulgrim charges at the nearest zombie, bellowing the name of Clanggedin, and swings furiously at it with his axe.

Attack: 7 Damage: 9

(Do we get an opportunity attack against the zombies that left melee?)

Guess, it was time to remove the Spikes, so, everyone could enter the room. Finna shook her head, loosing concentration and allowing the spell to drop. Still, if any kind of enemy is in the shooting range - she will send another bolt: Attack: 7 Damage: 10

OOC: You can indeed take an opportunity attack against one of the zombies that's moving away.

Attack: 26. Damage:9

(On phone so nothing fancy)

Roland attacks the zombies again, hoping to cut them down before focusing on the floating skull.

Attack: 22 Damage: 12

Bonus Attack: 17 Damage: 3

Sneak Attack: 5

Nemean takes out his scimitar and darts towards the nearest zombie, and slashes at the creature.

Attack: 26 Damage: 5