For a hot minute there, Knights looked like they'd be a format-defining tribe in Standard. Then all the other broken cards of Throne of Eldraine, like Oko, Thief of Crowns, Once Upon a Time and Fires of Invention, overshadowed them.
Oko and Once are gone now, so maybe it's time to give Knights another look. Mardu Knights gets to play format staples like Knight of the Ebon Legion, Fervent Champion and Murderous Rider, while boosting them with Inspiring Veteran and The Circle of Loyalty.
Fires is still around though, so you need to be fast. Embercleave turns any attacker into a game-winning threat, and the Adventure half of Smitten Swordmaster can close out the game if your opponent stabilizes the board.
Once more unto the breach!