SpreeSpree is a static ability found on some modal spells (see rule 700.2) that applies while the spell on the stack. Spree means “Choose one or more modes. As an additional cost to cast this spell, pay the costs associated with those modes.”
Cards with the spree ability have a plus sign icon in the upper right corner of the card, and use a plus sign (+) rather than traditional bullet points. These symbols are a visual reminder that this card requires an additional cost to be cast, and do not have additional rules meaning. (CR 702.172) (Choose one or more additional costs.)
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— Put a +1/+1
counterTo counter a spell or ability is to cancel it: remove it from the stack without resolving it. A counter on an object or player is instead a marker that changes characteristics or interacts with rules or abilities; for example, a +1/+1 counter modifies a creature’s power and toughness. (CR 701.6; 122.1) on target creature. It can't be blocked this turn.
+
— Target artifact or creature's owner puts it on their choice of the top or bottom of their library.