Target creature gets +1/+1 and gains first strike until end of turn.
The time between spotting a leonin shikari and feeling its claws is just time enough to draw your last breath.
Official Rulings for Seize the Initiative
1/1/2011 : A creature that gains first strike after other creatures with first strike or double strike deal combat damage in the first combat damage step will still deal damage in the second combat damage step.
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