Hoard of the Dragon Queen [IC. 2014 rules]

Dragon str save 26

While Draylin arms the ballista, Thistlewick and Montar both manage to land an attack on the fast-approaching dragon. For such a huge creature, the necrotic cantrip of the druid feels like the bite of a flea. Montar’s crossbow bolt feels like a toothpick between its scales, but at least it strikes deep enough. For a second, the blaze from the dwarf's fire rune envelops the dragon, but the beast moves in a spiral and shrugs off the chains with a mind-blowing fluidity, easily avoiding getting restrained.

Governor Nighthill and Escobert have moved toward another of the ballistas and spend their turns arming and aiming it.

The defenders of the third group have positioned themselves on the northernmost parapet. They too unleash a volley of arrows toward the beast.

Attack: 20 Damage: 5
Attack: 18 Damage: 9
Attack: 9 Damage: 10
Attack: 16 Damage: 7
Attack: 7 Damage: 9
Attack: 15 Damage: 6
Attack: 9 Damage: 6
Attack: 13 Damage: Unable to parse dice roll.
Attack: 8 Damage: 6
Attack: 6 Damage: 6

Over to Tam. Aiming the ballista and shooting it each require an action. 

[Can Tam use both of her actions, one to Aim and one to Fire? It seems like the Utilize action would still allow me the attack action. And the way you described it, one to load and one to aim and fire seems to support this. If this is wrong, let me know.]

Tam takes a deep breath and assesses the dragon, using her keen observational skills to line up a perfect shot. [using bonus action to activate Insightful Fighting. 12 Insight check versus the dragon's Deception to allow me to use Sneak Attack]

Aiming carefully, she unleashes a shot, not sure if it is good enough to hit [8 roll + 1 dex + 6 = 15 to hit the dragon with the Ballista. If I get proficiency bonus to that it is 17, but I doubt I do. In case that actually hits 22 damage + 9 for sneak attack in case that went through].

Because Draylin helped with loading it, the ballista actually doesn't need much aiming, so will allow both aim and fire as an action together. 

Dragon deception 16

Tam pulls the heavy trigger, and the giant bolt is released with a powerful snap. For a brief second, it looks like it might pierce one of the dragon's wings. However, sensing the danger, the creature folds its wings tight against its body to let the bolt whistle harmlessly by, before spreading them wide once again.

It hovers about fifty feet away from the parapets, and you all watch in horror as a bright, crackling light begins forming deep inside its chest. That electrical energy rises like a surge of lightning up its long neck and gathers into a violent ball between its jaws. It grows larger and larger until it erupts in a blinding line of lightning directly toward the defenders on the northernmost side (Group 3).

They each desperately try to jump aside to avoid the eviscerating breath weapon:
Dex saving rolls:
6
7
2
7
9
20
7
20
8
8

For those, who don't succeed, the lighting deals 53 damage. 

Recharge: 6

Only two of the defenders manage to jump away in time to avoid getting completely obliterated by the torrent of lightning energy, although they suffer severe burns. Even more worrying, the crackling light begins forming deep inside the dragon's chest again!

Leosin and another guard scramble over to the final unmanned ballista, working frantically to arm and prepare it.

Groups 1 and 2 unleash another volley of arrows, although they visibly struggle to aim their bows, too traumatized after the complete destruction they just witnessed:

Dice rolls because the dice roller is broken yet again:

Attack: 17 Damage: 6
Attack: 6 Damage: 7
Attack: 7 Damage: 3
Attack: 8 Damage: 3
Attack: 19 Damage: 5

Attack: 6 Damage: 9
Attack: 17 Damage: 7
Attack: 8 Damage: 9
Attack: 13 Damage: 9
Attack: 7 Damage: 7

Attack: 10 Damage: 5
Attack: 6 Damage: 5
Attack: 13 Damage: 7
Attack: 6 Damage: 7
Attack: 5 Damage: 6

Attack: 17 Damage: 8
Attack: 15 Damage: 5
Attack: 7 Damage: 4
Attack: 23 Damage: 5
Attack: 14 Damage: 7

Round 2

The air is thick with the scent of ozone, scorched flesh and burning stone. The blue dragon hovers 50 feet out, its throat pulsing with a brilliant, gathering electrical storm. Group 4 frantically attempts another round of attacks, although the hands of many tremble so hard they can barely pull their bows taut.

Attack: 15 Damage: 6
Attack: 7 Damage: 6
Attack: 10 Damage: 6
Attack: 18 Damage: 9
Attack: 13 Damage: 10

Attack: 5 Damage: 3
Attack: 19 Damage: 9
Attack: 16 Damage: 4
Attack: 20 Damage: 6
Attack: 14 Damage: 8

Thistlewick, Montar, and Draylin, you are up!

Draylin

"You got this, Tam.  He is fast, lead him just a tad.  Next one's got him for sure!"  The monk's hands moved in a blur, even as he offered encouragement to his ballista buddy.  His thin arms worked furiously at the crank, trying to ready another shot before the dragon could make another pass.

***ballista related activities and general encouragement ***

Montar maintains his focus, blocking out as the best he can the screams of the suffering. His aim is once again true, and he delivers a second crossbow bolt into the dragon's flesh (Atk: 21, dmg: 9).

Thistlewick runs over to the ballista Tam and Draylin are at.    'Wick takes a gamble...  "Let me know when you are about to fire!  I have a spell that might help..."

'Wick will do 99% of the spell work for Heat Metal  - holding back the final activation phrase until the ballista is fired. 

11 pt of fire damage upon contact with the bolt's superheated tip.
  
(( and as long as Wick's concentration holds AND the bolt gets embedded in the dragon's body...  Wick gets to bring forth additional fire damage each future round ))

Montar's bolt once again finds a weak spot between the dragon's scales. While Draylin and Thislewick help Tam with the ballista, Governor Nighthill and Escobert have finally managed to arm and aim theirs. With a resounding CRACK, the huge bolt is released from the second ballista, cutting through the air with an ominous hiss straight toward the hovering monstrosity! Attack: 12 Damage: 21

The bolt flies so wide into the dark, smoke-filled sky that the dragon doesn't even notice it! A collective groan goes up from the nearby guards as Governor Nighthill curses under his breath as he begins arming it again. It is up to Tam to finally set things right!

Tam closes her eyes and takes a deep, steadying breath. She looks over and sees the dead and singed men and women from the dragon's first strike. Flashes from the first terrible bolt of lightning replay in her mind's eye. She shudders. She MUST make this bolt fly true.

Her eyes scan the sky, watching the creature, carefully. She watched how it retracted it's wing last time. How it dodged the Governor's attack. Maybe she can anticipate it's next move. [22 insight roll for insightful fighting vs deception check]

Then she turns to the ballista. She was not used to combat at all, and especially not siege equipment, but she tried to think of this as her hand crossbow. She tried to think back to her training with the little thing. Her target practice, shooting the little bolts. This was the same thing, right, just at a larger scale. She took a deep breath, aimed, and fired! [Hot damn! Rolled a 17 + 6 + 1 dex = 24!! 15 damage (terrible) but we get the 11 fire damage if it hits and hopefully sneak attack of 4 (wah wah)]

Dragon deception: 6

The bolt snaps free, perfectly aimed this time. The heated metal tip flies through the air like a beacon of hope before it crashes violently into the creature's body, burying itself deep inside its scaly shoulder!

The dragon roars in pain -  a deafening, primal sound that makes every single cell in your bodies shrivel with fear. But even as it reels from the heavy impact, the raw fury in its eyes boils over. It violently snaps its head down and unleashes another blinding torrent of crackling energy that tears across the battlements, completely singeing another group of defenders (Group 1).

Dex saving throws:
8
1
16
9
2
2
18
3
17
16

Those, who don't succeed take 55 lightning damage. 

Recharge: 5

The defenders from Group 1 are caught completely by surprise and are utterly disintegrated, not a single soul managing to escape the deadly torrent of lightning breath. Where a line of brave guards stood a moment ago, only scorched stone and drifting ash remain.

To make matters worse, a collective horror grips the surviving parapet as the blinding, blue-white energy begins gathering in the dragon's chest yet again! The sparks are already licking at its jaws, defying all odds.

Over on the far side of the wall, Leosin and the guard helping him frantically yank the lever to fire their ballista at the hovering nightmare!

Attack: 25 Damage: 23

Group 2 unleash another torrent of arrows:

Attack: 8 Damage: 10
Attack: 8 Damage: 6
Attack: 13 Damage: 6
Attack: 5 Damage: 3
Attack: 14 Damage: 7
Attack: 5 Damage: 10
Attack: 17 Damage: 6
Attack: 16 Damage: 9
Attack: 15 Damage: 8
Attack: 7 Damage: 6

Leosin's heavy bolt flies after Tam's, ripping through the smoke and slamming directly into the dragon's chest with a resounding THUD. 

Round 3

A collective cheer breaks through the terror on the parapet. Blue blood splatters across the grey stone walls as the dragon violently jerks back in the air after taking two significant hits. Seeing this sends a sudden jolt of adrenaline through the remaining guards. Group 4's trembling hands steady on their bows as everyone realises that the monster can actually bleed!

Attack: 5 Damage: 8
Attack: 14 Damage: 7
Attack: 12 Damage: 9
Attack: 6 Damage: 10
Attack: 5 Damage: 10
Attack: 9 Damage: 8
Attack: 11 Damage: 5
Attack: 6 Damage: 3
Attack: 16 Damage: 8
Attack: 9 Damage: 4

The dragon is now visibly bleeding from multiple deep punctures, and it looks absolutely PISSED. The majestic, arrogant look it had when it first dove out of the clouds is completely gone, replaced by pure, feral rage. Its tail thrashes violently against the stormy sky, and the lightning gathering in its throat is sputtering and crackling with volatile fury. Over to Thislewick, Montar and Draylin once more. 

Draylin

The half elf was beginning to get the hang of the ballista.  His thin arms pumped furiously against the resistance of the crank.  Sweat was running down his face when the audible 'click' of the the siege weapon could be heard.  He risked a quick glance at the dragon as he turned to grab the massive projectile, smiling briefly as the beast's blood fell like rain.  In short order the contraption was set.  He stepped back, looking at Tam with a nod before turning his gaze back to the sky and hoping with all his heart that Tam and Leosin would fire true once again.

(( Bonus Action )) Thistlewick's Heat Metal is the gift that keeps on giving.   The ballista bolt buried in the dragon's chest continues to cause damage internally.

16 pt Fire dmg !

He is upset that he has one.... ONE spell casting left.. which he should hold in reserve for healing or hiding.   So, he uses one of his cantrips Minor Illusion to throw a 'sound' 30 ft away along the parapet.   The sound of drums.  Pounding out the pace for marching troops.  Encouraging real troops to stay the course.  To counter some of the dragon's bluster.

Then goes back to helping load up the ballista again.