We see Smaug sitting on the edge of a lake holding a guitar. He's tuning the guitar. After he finished Tuning it he starts to play and sing.

 

Smaug:"Oh, misty eye of the mountain below"

An army of orcs and other creatures are outside of Erebor.

Smaug:"Keep careful watch of my brothers' souls"

Dave is staying in front of Smaug's grave. Dave's wearing an eyepatch over his right eye and he has a big scar on his left cheek.

Smaug:"And should the sky be filled with fire and smoke."

Dave is in a city killing some orcs and the city is on fire.

Smaug:"Keep watching over Durin's sons."

A toddler Darksmoke and Dagahra run over to Kobayshi and she picks them up.

Dave is traveling through a forest. 

Smaug:"If this is to end in fire."

Dave slams the top of a table that has a map of the realm on it.

Smaug:"Then we should all burn together."

Dave is in dragon form and he's surrounded by orcs.

Smaug:"Watch the flames climb high into the night."

Dave is looking at a bright red stone that is pulsing. 

Smaug:"Calling out for the rope
Stand by and we will
Watch the flames burn on and on
The mountain side, hey."

Tanya is sitting in front of the throne of Erebor. She's just staring at it.

Smaug:"And if we should die tonight."

Dave is reaching out to Smaug. Smaug is smiling at Dave and he turns to dust.

Smaug:"Then we should all die together."

Tanya is holding onto a bleeding Violet.

Smaug:"Raise a glass of wine for the last time"

Everyone is in a dining hall holding up a glass.

Smaug:"Calling out for the rope
Prepare as we will
Watch the flames burn on and on
The mountain side
Desolation comes upon the sky."

Dave is back in the human realm and he's point a sword forward, yelling.

Smaug:"Now I see fire
Inside the mountain
And I see fire
Burning the trees
And I see fire
Hollowing souls."

Dave is facing against Evil Dave.

Smaug:"And I see fire
Blood in the breeze
And I hope that you remember me."

Dave is holding the hands of Darksmoke and Dagahra. They're all standing in front of Smaug's grave.

Smaug:"Oh, should my people fall
Then surely I'll do the same."

Dave is leading an army towards a big city.

Smaug:"Confined in mountain halls
We got too close to the flame"

Dave is sitting on a chair in a bed room holding onto the stone of Smaug.

Smaug:"Calling out for the rope
Hold fast and we will
Watch the flames burn on and on
The mountain side
Desolation comes upon the sky."

Visha is on the ground crying while holding onto bloody Violet.

Smaug:"Now I see fire
Inside the mountain."

Dave is talking to Tohru and they both look angry.

Smaug:"And I see fire
Burning the trees
And I see fire
Hollowing souls
And I see fire
Blood in the breeze
And I hope that you remember me."

Merlin is holding onto a flower made of fire.

Smaug:"And if the night is burning
I will cover my eyes
For if the dark returns."

Smart Smaug is sitting at a desk with many papers scattered about.

Smaug:"Then my brothers will die
And as the sky is falling down
It crashed into this lonely town
And with that shadow upon the ground
I hear my people screaming out."

We see everyone screaming out.

Smaug:"Now I see fire
Inside the mountains
I see fire
Burning the trees
I see fire
Hollowing souls
I see fire."

Dave is on the ground injured as Evil Dave is slowly walking towards him.

Smaug:"Blood in the breeze."

Dave is on his knees in a field of dead soldiers.

Smaug:"I see fire
Oh you know I saw a city burning out (fire)
And I see fire."

Megumin and Ilulu are sitting on the a cliff side.

Smaug:"Feel the heat upon my skin, yeah (fire)
And I see fire (fire)."

Dave is talking to his army.

Smaug:"And I see fire burn on and on the mountain side."

Smaug does a final strum on his guitar. Then he stares out to the lake.

Smaug:"You've finally come.....

Dave."

The Smaug Movie: Battle For The Smaug-Verse