Hoard of the Dragon Queen [IC. 2014 rules]

Montar's fragile calm threatens to shatter, as the shouts and screams of the townspeople are transformed in his imagination into the death cries of his clan, cries he never heard but nevertheless occupy many of his nightmares. They nearly undo him, but the enlarged dwarf barely holds on. As does his luck, as his next bolt also hits true, and powerfully so (Atk: 19, Dmg: 14).

Despite his internal struggles, Montar manages to shoot another well-aimed bolt at the dragon. The colossal beast shakes its wings in agony, hit not only by the dwarf's pinpoint attack but also by a continuous, agonizing stream of blazing magic lingering from Thistlewick's spell. 

Escobert attempts to use the moment and shoot with the second ballista. Attack: 10 Damage: 12

In his frantic haste, the massive machine violently kicks back as the heavy bolt is released, sending the projectile flying wide into the night sky once again. Escobert curses loudly in dwarvish, kicking the wooden frame of the siege weapon in frustration. It is again Tam's turn!

Another flash of lightning and another dozen people disintegrated right before her eyes. This couldn't be happening. She was going to wake up and this was all going to be a terrible nightmare. Wasn't she?

But no, she shook her head. She had to stay focused. This was no time for childish fears or squeamishness. She had to help defeat this monster. She had the creature's moves down, now, and if she could hit it, she knew she could make it count. So she took aim and loosed another shot from the ballista, but her nerves proved too powerful and her shot went wide.

[Rolled a 6 + 6 + 1 = 13, so not enough to hit. Sorry.]

The dragon's eyes narrow as it watches the giant bolt fly at a safe distance past its head and its attention falls on Tam behind the ballista and the two humanoids around her. Taking a deep, terrifying breath, the beast opens its mouth and unleashes the pent-up lightning energy directly towards the three adventurers!

Tam, Draylin and Thislewick, please give me a dexterity saving throws. DC 19. On a failed save, each of you takes 12, on a successful one - half of that. 

Then, before anyone can even clear the smoke from their eyes, the creature powerfully flaps its wings and propels itself towards the very top of the keep. It swings its massive tail in a brutal arc,  dealing 18 damage directly to the tower structure.

The impact shatters the masonry, sending a dangerous rain of stone pieces and broken tiles crashing down towards the defenders stationed there, wounding 1 of them in the chaos. 

Before anyone else has a chance to react, the dragon flaps its wings powerfully once more and disappears high above the clouds. You all hear its roars of wounded pride and body echoing through the night as it finally flies away, abandoning the siege.

Tam tries to leap free of the ballista, but her foot catches and she can't get free. She takes the full brunt of the blast, the lightning singing the ends of her hair as she falls backward. She's still up, but it takes a lot out of her.

"You  better run, you disgusting wyrmling," Tam yells in draconic after the fleeing dragon (it sounds like a better curse in draconic.

Montar screams his displeasure in Giant. "Coward! Stay and die!" "He fires off a shot, but misses short (Atk: 8). It takes the dwarf a few moments to calm down.

The falling stone does eventually snap him out of it, and, while he's still of large size, he runs over to the tower and attempts to, at minimum, keep it from dropping further chunks of stone on anyone. (Mason tool use: 25)