Mystical D20

Roll a D20. This card costs X cast equal to the D20. Roll again. This card does damage equal to the roll
to target creature. Roll another D20. If you roll a
20, target player loses 5 life, mills 10 cards then
exiles them, and you gain 6 life.
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A D20 is able to shift reality, restart a universe, or even
end one. Or the user could slip on a banana peel, fall ten flights of stairs, and die of a bee sting.