(fine! This feels like black ops 2...)
"Fine, if this is how it has to be..." Syren puts his hand on Alex's shoulder. "Soul Resonance!"
Alex stops as she feels heat flood her limbs. Her body begins to glow red. When she turns to say something, she sees a vision of the past. Images start flashing before her eyes: Zack as a child, holding a fish he had caught. Zack showing off his new assault carbine to a teenage Syren. Zack riding a new Kawasaki. Etc.
"now, let's get this going." Syren closes his eyes and thrusts his hand towards the horde of rising dead. "light, dark, they are mirrors of each other. When one ends, the other begins. But the line that defines each is distinct and never waving!"
The wind kicks up as Syren glows white, his eyes open and shining.
"Final Solace.... Supernova."
The air around Alex and Syren crackles with white lightning as a shield expands from his chest. Suddenly, the shield flares out, cleansing the air, purifying the putrid wasteland. As the shield rushes towards the epicenter of the blast, it hits undead warriors from both sides. The bodies are hit by the wall of light and vaporized, leaving behind blue orbs of soft light. The wall of light collides with the beam of ghastly green and creates a screeching sound. After seconds of resistance, the beam gives way, wiped out by the wall of light.
Syren releases Alex as his shield returns to his body. He sags his shoulders, utterly spent. The soft blue lights left behind by the dead begin to rise towards the clouds, peacefully.