Flavorwise, it's collecting "import duties" on magical effects
One of the more exciting additions to Magic: The Gathering formats over the years was the release of Planeschase
1 Repudiate // Replicate
During the invasion, the trapped planeswalkers got together with Ravnican leaders to strategize
For example, certain decks can play cards or bring back cards from your graveyard, making your graveyard essentially a second hand and giving you access to card advantage that way
Black Cat, Cunning Thief Common Crook The Death of Gwen Stacy Eddie Brock Gwenom, Remorseless Inner Demons Gangsters Merciless Enforcers Morlun, Devourer of Spiders Parker Luck Prison Break Risky Research Sandmans Quicksand Scorpion, Seething Striker Scorpions Sting The Soul Stone Spider-Man Noir The Spots Portal Swarm, Being of Bees Tombstone, Career Criminal Venom, Evil Unleashed Venomized Cat Venoms Hunger Villainous Wrath Angry Rabble Electro, Assaulting Battery Electros Bolt Gwen Stacy Heroes Hangout Hobgoblin, Mantled Marauder J
