If getting those spells into the graveyard helps feed my creatures however, then I can see the value
This card is every creature type
In addition to denying opponents resources, these decks often include flexible cards capable of accruing value through card draw and/or token generation whilst doubling as removal, often in the form of Planeswalkers or high-value creatures
As such, that entire period of the game became known as "Necro Summer," where all Competitive decks were using Necropotence or were specifically designed to counter it
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