Legolas, Counter of Kills

Reach
Whenever you scry, if Legolas, Counter of Kills is tapped, you may untap it. Do this only once each turn.
Whenever a creature an opponent controls dies, put a +1/+1 counter on Legolas.

"Two?" said Legolas. "I make my tale twenty at the least."

The Lord of the Rings: Tales of Middle-earth

"Do this only once each turn" lets you choose whether or not to untap Legolas as the triggered ability resolves. If you don't untap it, the ability will trigger again the next time the condition is met. Once you choose to do so, the ability will no longer trigger for the rest of the turn.