Aryel, Knight of Windgrace

You can tap any untapped Knights you control, including ones you haven't controlled continuously since the beginning of your most recent turn, to pay the cost of Aryel's last ability. However, you must have controlled Aryel continuously since the beginning of your most recent turn in order to use either of its activated abilities.

Tapping Aryel to activate either of its abilities while it's attacking doesn't remove it from combat.

If the target creature's power is greater than X as Aryel's last ability tries to resolve, the ability doesn't resolve. You can't tap extra Knights once the ability has been activated.