It is played in pretty much every deck that plays red and is always a card one has to play around if the opponent has a Mountain up
Honestly, while card advantage is always good, I think this card is so popular simply because people are fans of Korinna
Rodolf Duskbringer Rodolf Duskbringer lets you turn your lifegain into a means of reanimation during your end step

Scientists Academy Elite Academy Loremaster Academy Wall Accumulated Knowledge Acquisition Octopus Aeon Chronicler Aether Channeler Aether Syphon Airborne Aid Alandra, Sky Dreamer Alchemist's Apprentice All-Seeing Arbiter Alphinaud Leveilleur Amass the Components An Unearthly Child Ancestral Reminiscence Aphetto Runecaster April O'Neil, Hacktivist April O'Neil, Live on the Scene April, Reporter of the Weird Aquitect's Will Arcane Denial Arcane Investigator Arcane Subtraction Archive Haunt Archivist Archmage Ascension Archmage Emeritus Archmage of Runes Argent Mutation Arrester's Admonition Artful Looter Artificer's Epiphany Artistic Refusal Ascendant Spirit Assassin Gauntlet Astral Wingspan Astrologian's Planisphere Atemsis, All-Seeing Atlantean Cavalry Atlantean Skirmisher Attuma, Atlantean Warlord Aura Finesse Aven Fisher Avian Oddity Azami, Lady of Scrolls Azure Mage B.O.B

First thing's first, once you pick up your first deck of Magic: The Gathering cards, you're now officially a plane-hopping battlemage known as a Planeswalker