how do weapon evolutions work in vampire survivors?

Three things have to line up: the weapon at max level, its paired passive item in your build (any level), and then you open a chest from a boss/elite after the 10 minute mark. If all three are true the chest gives you the evolution. Few to start with: Whip + Hollow Heart = Bloody Tear Magic Wand + Empty Tome = Holy Wand King Bible + Spellbinder = Unholy Vespers Garlic + Pummarola = Soul Eater The catch most people hit is opening a chest before 10:00, it just gives normal upgrades. Once you've done one, the collection menu shows the recipe so you don't have to remember them.