First, it's a cheap instant, so you can cast it regularly, or put it on an Isochron Scepter
Meanwhile Pernicious Deeds and other such sweepers can control the game or clear a path, and your destruction awaits
Dust to Dust is great for handling artifact-laden strategies, while Blue Elemental Blast and Mirror Universe are great against burn decks and aggressive creature strategies
The fact it's Spiders and legendary creatures means you could also use this to enable certain things, Shalai and Hallar for example would go nuts with this and a bunch of Spiders
The Omen would probably be a playable card in this set on it's own since it's a nice way to fix
You can only get rid of as many cards as there is generic mana in the delve spells cost, so if you want to get rid of cards in your graveyard for some reason, youll need to find another way