Magnus Ursus

Okay, it's actually Apex Ursus, but magnus means huge or powerful and making giant bears is what this deck is about.

It's a variant of the GB enchantment deck that replaces Deepwood Grizzly with Possessed Ursus. It's the same cost but it scales way better when enchanted. The Apex Predators become huge threats really easily in this deck as well, giving you a 19/X after an Ursus takes just one hit, but they also work really well with anything else you can enchant. The Pipers are good buffs pre-enchant and can help sustain Ursi or Predators. Ancient Herald is also really good in this deck because his effect works for almost every creature in the deck, so he always gives quick value, and he doesn't require enchant to be a threat, making him a solid opener.

I almost always go midrange to challenge my opponent's wells and try to establish a good forest where I can play an Ursus then dash it to their orb with horsemaster. Usually, you'll win by taking people from full -> 0 in one or two hits.

This deck is a monster against red or green decks, which simply don't have good ways to deal with your Ursus without sending its attack through the roof. Blue is a bit trickier because of Frogify but you can bait it easily. Rush isn't too bad because of your taunt, but it can be hard to get your enchants going while keeping land control. For this reason, and because Yellow events can be really fast, I recommend adding some earthcrafts to the base list and dropping a couple of other cards (I run 1 Frogify and 2 Piper, but you could also drop an apex/enchantress or the heralds if you hate him). If you want to have fun you actually can throw Magnus in, but he's expensive and not as generally useful as Tethera.

Mulligan is Herald, Willow, Ursus, Piper, Horsemaster, Enchantress in order of preference.
Probably get rid of any Apex, Tethera, or Feed in your starting hand, but keep everything else.