The meat of the stream as far as Horizon goes was developers talking in detail about the mechanics of the game. They talked while the trailer played in the background, giving commentary on specific things. They went into detail about game mechanics, the abilities of the enemies, and Aloy (also how to pronounce her name).
They put a camera on Thundermaw as it sat in idle animation, in the environment the trailer takes place, while a dev talked about stuff. This idle animation of thundermaw was the only unique Horizon footage. It showed all of the damage it sustained over it's life from tribes it crossed. A significant amount of spears all over it's body. Sparks flying near damaged parts of it's body that revealed the delicate electrical innards.
These Thundermaws have a ton of abilities, it's up to Aloy to decide which ones she will take out if she feels like hunting Thundermaws for some reason. The one in the trailer was damaged so it couldn't do but so much as it had features that stopped working due to it's damage. This effectively made it a lower level Thundermaw compared to a fully whole thundermaw which just sounded overpowered by what the developer described that this thing is capable of. She shot the disk launcher that it used on her and turned it back on it. When she slides under it she's shooting stamina canisters which makes it so the Thundermaw can only do a few of it's abilities. They also mentioned that you can just run away in this situation, but it wouldn't make for a good presentation given the time they had. While running you can set up traps and whatnot if you still want it taken out or slowed.
Just ask about the information from that stream, that's all that was new. He did confirm that you would be able to go to the broken city that's showed at the end.
