Clockwork Beast, and thus the clockwork mechanic, dates back to Alpha. Clockwork creatures come into play with a number of counters and lose them for attacking or blocking. They also have some way to put counters back on if they lose them. The problem is that they’re all so expensive to cast that they never see play. I suppose they would be interesting in a casual green/artifact deck with Doubling Season but there are better uses for Doubling Season.
The only Clockwork creature I ever played was Clockwork Hydra. A 4/4 for 5 wasn’t bad in Time Spiral draft or sealed, particularly when you could slowly make him bigger and eventually break the creature stalemates that sometimes occur in limited play.
Manipulate Fate could be used to thin your deck of land or other cards when you are trying to assemble the last pieces of your combo. It was also much better before they changed the “out of play” rules. Previously a Wish such as Cunning Wish or Burning Wish would have been able to retrieve these cards but now they can only retrieve cards from your sideboard. These wishes find cards that are “outside the game” and the exiled zone that Manipulate Fate adds to is still inside the game. This is one of several rules I don’t agree with from either playability, ease of understanding or flavor perspective, but Wizards hasn’t asked me for my opinion yet.
You could probably work really hard to find a combo with Manipulate Fate and Riftsweeper or Mirror of Fate but this seems like a really awkward way to try to set off a combo. If you’re playing Manipulate Fate then you’re already playing blue and you’re already either playing Vintage, Legacy or casual. In all those formats there are much better tutoring and card drawing options in blue.