The Battle of Bhati
The oni just laughs and laughs as Dharmesh's spell strikes him, only to fizzle out of existence.
But then Damien begins his solo rock concert, and the army just...stops and stares. Some of the oni actually drum along with his music, though it's drowned out by the sound of his guitar. The fireworks light the sky in a multicolored array of flame. He hits the crescendo, and a wave of sound explodes out from him, sweeping over the army.
The front wave bends and breaks, sound that could shatter stone picking most of them up and sending them tumbling backward with the sheer force of the noise. The Voidlord stays standing, but he is in the minority, with the vast majority of the fiends and monsters being swept backward by the raw energy of the power cord he just struck.
An army strikes the wall of his power, and the army breaks.
But they reform quickly, and they have almost regained their feet and started the march again when Cassie appears in the sky above the army. She is wearing her simple blue robe, and her eyes are hollow black pits in her face. She spins a pirouette in midair, and laughs, and there's not a person in miles who doesn't hear that laugh echoing inside their skull.
You want to step back. Further. Quite a bit further, her mental voice speaks in Damien and Dharmesh's minds, with a cold, slithering undertone like nothing human lying beneath the girl's thoughts. She smiles at the army beneath her. And she opens a gate. Tears a hole in the world, leading...elsewhere.
At first, for a tiny fraction of a second, it's not obvious what she opened it to. There's just a black hole in the world. Then it fills with light. Light too bright to look at directly, the blazing incandescent flame of a star's core. The air turns to plasma. A wave of light and heat strikes the army in the next instant.
They don't have time to scream. They don't even die of anything, in the traditional sense. They just stop being there, the nuclear flame consuming them in a microsecond.
On the wall, the light blossoms brighter than the sun by far. Like looking into the light of Heaven, or of Hell's fiercest flame. Then the ground explodes, debris exploding outward. A fireball explodes outward, cascading up into the sky, followed by a mushroom cloud.
Then the blast wave hits. A wall of force, of debris and air and raw force, that makes Damien's tsunami look like a child's trick. The wall of the city explodes, absolutely leveled. It's not a question of remaining standing. There's nothing to stand on. It continues on, tearing up trees, shredding buildings. There's nothing left in its wake.
When the dust clears, and you've managed to stand up and get your bearings, there's no sign of the army. Not even bodies. There's just a crater. A crater some four thousand feet deep. A crater larger than the city, and overlapping it. Half the city is gone. The other half is largely leveled and engulfed in a firestorm. The air is filled with smoke, dust, and ash. Miles away from the city, you can still see the mushroom cloud hanging over Bhati.