Fathomless descent Souls of the Lost's power is equal to the number of permanent cards in your graveyard and its toughness is equal to that number plus 1
This is the crux of the question to me
Its good for green decks that are low to the ground, even in a format with Llanowar Elves
Wilds of Eldraine (WOE) #51 Illustrated by Chris Seaman Magic: The Gathering, MTG Company: Wizards of the Coast Brand: Magic The Gathering Item Type: Single Card Release Date: September 8, 2023 Series: Wilds of Eldraine UPC: Stock #: 451731 Our Guarantees to You, Our Valued Customer
Against the blue decks you generally want to save it for their end step, against the aggro decks you want to combat step it, while against the midrange decks its often best used in the upkeep just to tap down lands (Tron literally cant interact at anything other than Sorcery speed)
Forcing them to choose between attacking or casting a spell that turn feels like youve given them only half of a turn