"Berserkers! We and the gods have joined forces with Magic: The Gathering to bring you a first look into the new Viking inspired card set, Kaldheim," says Swedish melodic death metal band Amon Amarth.

"This is Magic's most metal set yet and ready for your next raid on the card battlefield! Tune in on January 7th, 2021 at 9am PT on Magic's Twitch channel for the full reveal." 

According to Wikipedia, Magic: The Gathering is a collectible and digital collectible card game created by Richard Garfield. Released in 1993 by Wizards Of The Coast (now a subsidiary of Hasbro), Magic was the first trading card game and has approximately thirty-five million players as of December 2018, and over twenty billion Magic cards produced in the period from 2008 to 2016, during which time it grew in popularity.

Each game of Magic represents a battle between wizards who cast spells, use artifacts, and summon creatures as depicted on individual cards in order to defeat their opponents, typically, but not always, by draining them of their starting life total. Although the original concept of the game drew heavily from the motifs of traditional fantasy role-playing games such as Dungeons & Dragons, the gameplay bears little similarity to pencil-and-paper adventure games, while simultaneously having substantially more cards and more complex rules than many other card games. 

Certain cards can be valuable due to their rarity in production and utility in gameplay, with prices ranging from a few cents to thousands of dollars.