There are three of these effects available, presented here as a way to make the deck go into turbo
The main one is Anowon, the Ruin Thief, a card that not only buffs your tokens, but you can mill your opponents and sometimes draw cards
For limited promos and cards with unique specifications, it can be difficult to grasp the entire picture unless you look at the volume of listings and variations on the Japanese side
Higher-power decks can also include Thassa's Oracle or Jace, Wielder of Mysteries for their own win conditions, which incidentally means that milling an opponent out could mean that they win the game
Conversely, with Chronomaton the problem was that youd invest a lot of time and mana into a creature, and then when you finally got around to trying to do something with it your opponent could just kill it and youd have nothing to show for it but Hangarback Walker is very much the opposite unless your opponent has just the right removal spell
Certainly still a card well worthy of cube in terms of power but none the less one of the most overrated cards on the list