The ability goes on the stack before blockers are declared, which means your opponents have a window to respond
TPC says that the upcoming set will depict monsters "during different moments throughout daytime and nighttime." Artists visible throughout the trailer include 0313, Amelicart, Aspara, Yuu Nishida, Whisker, Iori Suzuki, and 5BanGraphics
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For instance, Forces of the Imperium are filed under White and rely on building large armies (which is fitting, considering its in-universe attitude that there are always more bodies to use as canon-fodder for the Emperor)
Typically, double strike is best when it allows your creatures to hit first, hit twice as hard, and survive combat while making sure your opponent and their creatures dont