I have a thornscape familiar in play and then I cast the thornscape battlemage with the red kicker. Does the battlemage cost 3 or 4?
The color of a spell is determined by the mana cost listed in the upper right of the card.
Additional costs such as kickers have no effect on determining the color of the spell.
Therefore, the Thornscape Battlemage is a green spell and gains no benefit from the Thornscape Familiar. The cost is 4(2G + R kicker).
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