While its adventure isnt overwhelmingly good, its still nice to be able to put this card in exile early and protect it from being forcibly discarded
Simply flash a bunch of creatures in prior to your turn, play spells as necessary, hit an opponent with your creatures, untap your lands, and you essentially have free mana to do the same thing again
Both halves matter against a deck like Dimir, but the fact that one half will matter against most decks means this is likely maindeckable
You might also want to include as many orcs and goblins as you can for sacrifice fodder
This is because Garth can be tapped in order to allow its controller to cast a copy of one of six spells: Disenchant, Braingeyser, Terror, Shivan Dragon, Regrowth, and even the famed Black Lotus