Atheon would ALWAYS win. He can't leave the Vault, so the battle would HAVE to take place there. To do any kind of damage the other two would need to travel through time, grab the relic, kill the oracles [i]all by themselves[/i] and then come back. Again, Atheon controls the Vault and therefore controls everything inside it. Even if Crota (and Skolas in a way - servitor bonds) can't be damaged, there's the Oracles. And if they would have to go through the entire Vault to get to Atheon, there's the Gorgons. Skolas can't taint any of them because he can only taint light, and neither Atheon or Crota has light. Logic here; would Skolas and Crota really be able to fit back through the portals and get back to Atheon? And who would open the portals in the first place? TL;DR Atheon always wins and anyone who says otherwise is a Christmas noob