Magic: the Gathering - Dominaria United Collector Booster Display Box 3200MHz Walker Trejo is spawned by

Walker Trejo is spawned by its specific Zombie cards (which also contain a few "Trejo Rush" copies that activate him as soon as he spawns)

The vast majority of humanity was turned into slathering

In this asymmetric combat game

Details on all known holidays in Equestria

Magic: the Gathering - Dominaria United Collector Booster Display Box 3200MHz Walker Trejo is spawned byThe Dominaria United Collector Booster Box contains 12 Dominaria United Collector Boosters and 1 Traditional Foil Box Topper card. Each Collector Booster contains 15 Magic: The Gathering cards and 1 Traditional Foil double sided token, with a combination of 56 cards of rarity Rare or higher and 45 Uncommon, 4 Common, and 1 Land cards, with a total of 1013 foil cards. Foil Borderless Mythic Rare Planeswalker in 2% of boosters Contents: 12 Dominaria