@FanOfMostEverything  
You’re right, I don’t think I’d thought through what +2/+2 and Horsemanship would do to the game; I just noticed Horsemanship, chuckled, and moved on. As it is, this card is an instant win in a lot of situations.
 
I’m still rooting for the card’s author bringing back Enchant World for this, though. This definitely feels like a world enchantment, especially being something that you don’t want more than one of in play, ever.
 
… Also, I just noticed the “creatures you control” provision, and I can’t say that I’m impressed. I liked the original model, where a card like this empowered all creatures of the relevant types, and you had to hope that none of your opponents was running Sacred Mesa, Conspiracy, or changelings.

@ExOttoyuhr  
Board was definitely invented for the purposes of this card. It’s not quite one-to-one with world enchantments, since noe player can get rid of another’s world enchantment by playing another. Implementing something similar to the legend rule would probably be best.
 
As for the effect itself… O_O Yeah, that’s way too cheap for a double-Anhtem effect that also makes your creatures nigh-unblockable. Even if you can’t play multiples, this is horrifying as is.

I’m not seeing anything about Board Enchantments in the game’s rules, but this could easily be an Enchant World.
 
Also fun to see Horsemanship again – one of the bigger flavor fails in the game… :)