If Alex Mercer from Prototype were to be a Servant in the Fate series, he would likely belong to the Berserker class. As a Berserker, he would be summoned as a powerful and near-unstoppable force, matching his aggressive and chaotic nature displayed throughout the Prototype games. His Noble Phantasm could be "Blacklight Devastation," where he unleashes a devastating wave of his iconic tendrils, capable of corrupting and consuming all it touches. This ability would reflect his immense power and destructive capabilities, making him a formidable opponent on the battlefield.