Red hate

Dragged straight back to hell by the clawed hands of scores of lesser devils, Zartak found himself securely back in his former prison.

It’s large and he has servants of course. Grandeur to suit his station but he is not allowed to leave.

A cage, no matter how gilded, is still a cage.

Silently he broods.

Silently he plots.

He shall have his revenge in the blue dragon.

He shall see her fall. 

Blue triumphant

No one was surprised when the war came.

What was surprising though, was the outcome.

The devil was more powerful and his army was larger in size.

Unfortunately his troops were neither as well trained or as loyal as he was used to, as a prince of hell.

His human armies deserted at the first opportunity.

Zartak was forced further and further back into the northern territories until he was finally cornered.

Thereanthor had come personally to lead her dragon-borns and Black cloaks.
Thousands of Dragon-borns had been unwittingly pulled back through to Fissa at the time of the portal rend.

They were loyal to her and grateful as she protected them from harm even as they threw themselves blindly forward.
Thereanthor had a secret weapon though.
A group of troops that she'd kept secret until that moment.
Tieflings.
Thousands of them.
Zartak had been unaware of his own contribution to his own destruction.
When he breached his section of the planar barrier, years before, the tormented legions of half human, half devils had been released into this world.
Despite their heritage, they hated all pure-blood devils.
A hatred they directed at Zartak.

Tens of thousands died in that last battle but it was the dragon herself who ended it.

Her jaws closed around the giant devil’s throat.

Her entire weight upon his.

Zartak wasn’t killed though.

You can’t kill an immortal.

His massive body crumbled into chalk-like pieces and his essence was pulled back to the pits of his fiery prison.

As his body coalesced, his screams of vengeance shook the gates of hell. 

Purple allegiance

After the resistance had been utterly destroyed, the Dragon and the Devil carved up the massive continent of Fissa between them.

Thereanthor took the southeast and Zartak, the northwest.

It was an acceptable agreement and suited both the devil and the dragon…

Initially.

Soon though, Zartak felt the need to expand his empire. He built up an army of slaves to equal that of his erstwhile partner.

Theranthor, being no fool, built up her defences in reaction to the devil’s growing forces.

War was inevitable.

Red assistance

Intelligent enough to understand the price to be paid, Thereanthor accepts the ‘assistance’ of the red skinned, devil Zartak.

After a month of organization the Black cloaks try again to breach the barrier from their side.

This time though, forces on Fissa work against them.

Armies of orcs led by mysterious leaders attack the mountain stronghold.

The shadowy Grey elves of the surrounding forests, harry them constantly.

The Black cloaks were forced to hire mercenaries to protect them. Tough but naïve adventurers.

These adventurers kept the Black cloaks safe and slaughtered hundreds of the strangely well-organised orc legions.

Still they came though.

There were thousands of them, supported by the arrows of the Grey elves and the aerial support of well-trained, giant eagles.

The magical barriers were about to fail but still the hired mercenaries held their ground.

The ceremony was ready.

A split in the fabric of reality appeared and widened.

Thereanthor sensing the rift, poured her primordial power into it. Pushing it further. Stretching it ever wider.

She could see her way through but the window was still too fragile. Still too small.

With a psychic message to Zartak, the once-prince of the underworld exploits the damage already done and struck at the barrier between worlds with his diabolic energy.

Under this triple assault, the barrier cracked.

Both Dragon and Devil seized their opportunity and slipped through the gap between worlds. 

Fiends in low places

Although unable to see anything from his prison, Zartak: the once prince of Hell, feels the assault against the planes in his immortal bones.

Something is trying to free itself from somewhere.

Something with power.

A dragon.

A dragon with the power to rock the barrier between planes.

…

But not enough to break through.

The devil smiles.

Whoever it was has failed.

It needs more power than it commands.

Zartak smells desperation.

Zartak smells opportunity.

Summoning an imp, the massive devil composes a message to his soon to be ally.

The dragon shall be free but at a price.

The price of his own liberation.

Enemies in low places

Deep in the pits of hell, a Demon roars in anger and frustration.
The Tiefling near its feet trembles and throws itself prostrate.
“What is wrong Master?”
The massive Demon looks down, fury painted like a mask across its broad features.
Snatching up the wretched Tiefling, the Demon raises it to its face.
“THE FEY GODS HAVE STOLEN MY PRIZE!”
“Do you mean the Human: Vogir? Surely he’s not worth this much anger?”
“NOT WORTH? NOT WORTH!”
Forcing himself to calm down, the demon takes a rattling breath.
“NOW THAT I AM TRAPPED HERE AGAIN, VOGIR WAS MY BEST CHANCE OF DEFEATING THE TREACHEROUS THEREANTHOR.”
“But surely Master, his mission hasn’t changed…”
“TRUE, HE WILL STILL SEEK OUT THE DRAGON, BUT HE’LL DO IT OF HIS OWN FREE WILL. I WILL GAIN NO SATISFACTION IF HE’S NOT A TOOL OF MINE!”
With that, the Demon bites the head off his unfortunate underling and tosses the remains aside.