Magic: The Gathering – The Brothers' War

From BoardGameGeek:

Get ready for a blast from the past as Dominaria's heroes must launch an expedition into ancient history in order to stop the New Phyrexian planar invasion in the present day! This Magic: The Gathering expansion uses time travel as a framing device in order to revisit the epic conflict first glimpsed in 1994's Antiquities in the form of excavated artifacts. Nearly 30 years of real-time later, the continent-destroying war between the two brothers, Urza and Mishra, is finally getting its time in the spotlight. The Brothers' War is packed with soldiers, armies, giant robots, and all the horror and destruction of mechanized warfare. It boasts two new mechanics: Prototype, which allows players to cast a less powerful version of an artifact at a lower mana cost; and Powerstones, artifact tokens that can tap for mana that can't be used to cast nonartifact spells. Joining them are the returning mechanics of Unearth (first seen in Shards of Alara) and Meld (first seen in Eldritch Moon). Similar to the Timeshifted cards in Time Spiral or the Mystical Archive in Strixhaven: School of Mages, there is a bonus artifact sheet in The Brothers' War: every booster pack of The Brothers' War contains a reprint of a classic artifact, from Magic's past, in the retro frame. Two preconstructed Commander decks featuring Urza and Mishra were released alongside the main set. Additionally, to play into the "giant robots" theme, this set also includes a crossover special in the form of 15 cards depicting characters from another Hasbro intellectual property about giant robots fighting: Transformers. These cards are not in draft boosters, but can be found in set boosters, collector boosters, and bundles.