Relentless Bravery

During each player's declare attackers step, after
that player has declared attackers, up to one
target creature you control gains indestructible
until end of turn, and attacks this combat if able.
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The raging fire within every soldier will ultimately
prevail, unleashing a relentless warrior with an
abundance of bravery; an indestructible weapon on
the battlefield that will show no mercy.