Grongir, Underway Avenger

Flash
When you are the defending player, creatures you control can attack during your 'declare blockers'
step. (You can't declare creatures attacking this way
as blockers. After your 'declare blockers' step, your opponent may declare their own blockers to block your attacking creatures.)
"They come this way again, lads, and we'll show 'em
the true meaning of a Dwarven grudge."