It gives you the option to tap creatures you control with a certain total power in exchange for an improved effect on cast
For example, thanks to the focus on reanimation, big-mana plays and board wipes, Smaug the Impenetrable makes for a great upgrade to the Hosts of Mordor Precon
Angel of Deliverance + Razaketh, the Foulblooded + Demon of Loathing
Basically any Graveyard deck that has cheap, repeatable sources of graveyard recursion: Shirei, Shizo's Caretaker is one such deck but I'm sure there's others
Bounce the Miner and make Ninth Bridge Patrol great again: Key cards: Aethergeode Miner, Ninth Bridge Patrol, Decoction Module and Decoction Module or Mirage Mirror
A 9/9 that blows up two permanents and draws two cards over the next few turns is absurd, though youll probably win before that point