Aryel, Knight of Windgrace

Mana cost: {2}{W}{B}
Type: Legendary Creature — Human Knight
Power / toughness: 4 / 4
Set: Commander Masters #336 (uncommon)
Price: $0.24 USD

Vigilance
{2}{W}, {T}: Create a 2/2 white Knight creature token with vigilance.
{B}, {T}, Tap X untapped Knights you control: Destroy target creature with power X or less.

Aryel, Knight of Windgrace has 4 printings, first in Dominaria (2018). EDHREC ranks it #8,197 among Commander cards. It appears most in Sidar Jabari of Zhalfir decks (9,301 on EDHREC). 1 public deck on TCG runs it. It has 4 official rulings.

Legality

commander: legal
legacy: legal
vintage: legal
pauper: not legal
modern: legal
pioneer: legal
standard: not legal
brawl: legal

Public decks that run Aryel, Knight of Windgrace

Cavalry Charge - March of the Machine Commander, led by Sidar Jabari of Zhalfir

Commanders that run Aryel, Knight of Windgrace most

Deck counts from EDHREC.

Sidar Jabari of Zhalfir: 9,301 decks
Syr Gwyn, Hero of Ashvale: 3,444 decks
Cecil, Dark Knight // Cecil, Redeemed Paladin: 259 decks
Arvad the Cursed: 38 decks

Often played with Aryel, Knight of Windgrace

Cards that show up in the same decks on EDHREC.

Rulings

2018-04-27: Once you announce that you're activating Aryel's last ability, no player may take other actions until the ability's been paid for. Notably, players can't try to make the value of X invalid by removing or tapping your Knights.
2018-04-27: 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.
2018-04-27: Tapping Aryel to activate either of its abilities while it's attacking doesn't remove it from combat.
2018-04-27: 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.