"Fear not the behemoth heard from miles away. Fear the stalking felidar, which reveals itself only for the kill."
—Rielle, the Everwise

Frondland Felidar

Vigilance
Creatures you control with vigilance have "{1}, {T}: Tap target creature."

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Frondland Felidar’s last ability applies to itself as long as it still has vigilance.

Once you’ve activated the ability granted by Frondland Felidar, causing the creature to lose that ability (such as by removing Frondland Felidar from the battlefield) won’t affect the ability on the stack.

Tapping an attacking creature doesn’t remove it from combat.

You can activate the ability granted by Frondland Felidar after attacking but before blockers are chosen.