Tainted Aether

• WWizards of the Coast2004-10-04
  Official Ruling
  If more than one of these is on the battlefield, the controller sacrifices a creature for each one of these.
• WWizards of the Coast2004-10-04
  Official Ruling
  If the controller has no other lands or creatures on the battlefield, they must sacrifice the creature that just entered.
• WWizards of the Coast2004-10-04
  Official Ruling
  Tainted Aether's controller is the one that controls its triggered ability, but the controller of the creature that entered chooses what creature they sacrifice during resolution.
• WWizards of the Coast2004-10-04
  Official Ruling
  If the creature changes controllers before this ability resolves, its new controller has to sacrifice something.

Rulings via Scryfall