Who is he?
Well, the answer is simple. He’s new. Sarthorael the Ever-Watcher is an entity created by Creative Assembly specifically for Total War: Warhammer. He’s designed to be a huge in-game challenge to anyone who makes it to the late-game of the campaign. He functions a bit differently depending on which faction you’re playing, though.
If you are Chaos, he is against you. Selected by Tzeentch to bring forth change, he will challenge you from the Chaos Wastes and repeatedly assault you until you deal with him. He will be a constant thorn in your side, and even then he’ll come back after being bested. Demons aren’t gone forever.
If you are anyone else? He is still against you. This time, though, he’ll be teaming up with Archaeon to storm down south and bring ruin to anything he can.
The best bet in either case is to have overwhelming numbers. He’s strong, so you’re going to take losses – there’s no getting around that. Just accept it and swarm him with spearmen or units dedicated to hero slaying, like Empire Witch Hunters. Alternatively, pound him with cannonfire. Cannons always work wonders.
Hopefully Sarthorael is a sign of things to come. I certainly wouldn’t mind more demons in the game. Maybe we can get greater demons as generals in the future? Or perhaps have them start popping up in multiplayer battles? I can dream.