When an exploit creature enters the battlefield, the controlling player may sacrifice a creature, potentially triggering an effect on that card or others
It made a lot of sense to bring Archenemy back for the Bolas arc: some players got to play as the plucky Planeswalkers of the Gatewatch, while another played as Nicol Bolas, spinning all matters of twisted schemes
If you want the same effect now, you have to pay (3)(U)(U), with Capture of Jingzhou or Temporal Manipulation
(Tales of Middle-earth was legal in the Modern format, but not Standard.) The Final Fantasy set is a big deal for Magic because it brings Universes Beyond into Standard, helping to usher in Spider-Man and Avatar: The Last Airbender sets later this year that will also be Standard-legal
As unwieldy as it may appear to us now, this was one of the best deals out there, because it was large enough to pose a threat and efficient enough to not slow you down and let you leave mana open, which left it all but impossible to kill