Sword of the Realms provides protection for your threats, which you can recast once they die and are equipped with the sword
You do need to use one mana of every color, but the deck can easily make your lands every land type to make this even easier
So, to some extent, Koth is an incentive to go Mono-Red or close to it, and if you can do that, obviously the -3 will kill most stuff, but on a board that is built out at all, your opponent can still easily deal with Koth This will be able to attack with higher power a decent chunk of the time for sure, but the times where it is just a lowly 2/3 will feel pretty rough
All I can say is that Animar really didnt need another card this good
Although it came out earlier in the year, Kaldheim is shaping up to be a set full of powerful cards for Standard, Commander, and Modern
This enchantment probably wont be the deciding factor, especially with a 3-mana price tag, but itll do a lot of work in those long and grindy games