The Blade of Arsenius

At the beginning of your upkeep, target creature
gains a +1 +1 counter.
Relentless: During your combat phase,
if a Terrasen creature attacks, you may choose
to untap all attacking creatures you control.
If you do so, after this phase there is an additional
combat phase.
The Blade is known far and wide as a mighty warrior,
though only the Royals have seen her face.