Plasm Capture - mtg.wtf

Instant

Counter target spell. At the beginning of your next first main phase, add X mana in any combination of colors, where X is that spell's mana value.

"Everything serves a purpose. Even you."
—Vorel of the Hull Clade

2013-04-15 If the countered spell had {X} in its mana cost, include the value chosen for that X when determining how much mana to produce. For example, if you counter a spell that costs {X}{R} with X equal to 5, you'll produce six mana.
2013-04-15 Your precombat main phase is the main phase that happens immediately after your draw step, not any other main phase.

Card is in preconstructed decks:

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