Hanging Gardens of Babylon (for those that don't like that title, just call it "Throne of Babylon" in your head
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Evil Fortress
II Kings 25:27-28
Identifiers: Plays to set-aside, holds 1 OT human and 1 Babylonian king
"Protect contents from opponents. If holding a Babylonian king, each upkeep you may exchange a Babylonian site in territory with a Babylonian in deck or vice-versa, or release a captured human to take it to territory and convert it to a Crimson Babylonian."
This is from the exile as recorded in II Kings 25. King Evil-Merodach released Jehoiachin, former king of Judah, from prison and hosted Jehoiachin in the palace with food, new clothes, higher stature, etc.
BabylonRed site
Same verse
Identifier: Babylonian site
"If your lone blocking Babylonian is removed from battle by an opponent, you may remove this site from the game to add your Babylonian king in play or set-aside to battle."
Comes with built-in interaction with Hanging Gardens of Babylon