Dust Animus

Plot abilities are written “Plot [cost],” which means “Any time you have priority during your main phase while the stack is empty, you may pay [cost] and exile this card from your hand. It becomes plotted.”

If a plotted card has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.

You can’t cast a plotted card on the same turn it became plotted. On any future turn, you may cast that card from exile without paying its mana cost during your main phase while the stack is empty.