The matchup was me (sedna) and a rook vs an erebus and an AI UB (player dropped at loading screen).

Anyway, soon after the match started, I went up in a fight against erebus for a flag. What happened there was suprising - he did a rediculous amount of damage. Now, I've fought a lot of erebus before. I've never complained about it, but this time, it just seemed overwelming. He appeared to have nightcrawlers and bite during the fight. I was forced to retreat, half health, about 4 seconds after engaging him.

I warned my teammate that he was doing incredible damage, and the game went on. As the game progressed, my teammate started accusing the erebus player of hacking (though I know it's impossible, from what I'm told by developers, any form of hacking would cause a desync), because he too was amazed at the damage he was doing.

The UB continued to feed us to the point where I had a mage slayer artifact, the 1500 armor, the 3000 crit armor, and the 1500 helm.

Yet that didn't help. Erebus arrived with a good backing of reinforcements, smashing through all our defenses by himself, as I attempted to pummel at him, retreat a 5 second walk back to my health crystal, and attempt again, several times to the point where he was just smashing at our citidel.

Erebus was not fed, with 2 kills, and was even level with us. I spammed the AoE damage heal, pounced erebus over and over, and couldn't stop the wrecking ball from coming through. We won the game, just barely as my rook teammate was capping both of the other team's portals and attacking their citidel while it happened.

So what the hell happened here? Give me some insight of how this player (that went by the name of shiro) played erebus with  an impossible to beat build?