Steven Seagal, Rain Dancer

Whenever a spell is cast during an opponent's
turn, you may tap Steven Seagal, Rain Dancer.
If you do, create a colorless Raindrop artifact
token with "Sacrifice this artifact: Add one blue
mana to your mana pool."
—
Steven Seagal has always been fond of the rain. It
brings him joy and inspiration to dance and play
among the drops.