I'm wondering if Royal Assassin has a place. Dies to Memnites, but can probably control most lord decks to death since each Assassin can off a Lord every turn if they're used.

I'm trying to theorycraft other ETB, dies, or continuous removal on threats to win the CA game.

Also, people have mentioned Surging Flames but Surging Sentinels is also a solid one. I think it might even take down Memnites.

The Assassin can defend itself vs lords, but how does it win?

Yeah, Surging Sentinels is another auto-win by turn 4, just as broken as Flames if you ask me. Since you get your blockers in your 3rd turn, no matter who's on the play you deny Memnites their winning attack unless you somehow get 4 lands on your first ripple.