Have you ever died from a Mana Crypt or ever seen someone taken out by one? Of course you have; we have all seen it happen or have been the victim of it. But the real question is, has Mana Crypt ever won you the game? And I'm not talking about Mana Crypt giving you infinite mana to do something crazy, but it alone actually winning you the game? Doubt that has ever happened. Well now it has, behold, an obnoxious death by Mana Crypt.
Kefnet the Mindful is quite a powerful commander and honestly, I am rather surprised that I have never seen anyone play him. For three mana, you get an indestructible 5/5 flyer but most importantly, he enables you have a super convenient mana sink allowing you to draw. While yes, four mana to get a single card isn't impressive at all, you will quickly change your mind with how easy it is to set up infinite mana in here giving you a chance to put your entire deck into your hand.
Alright, first of all there are a number of cards that we are looking for that help us out to get to our key pieces or provide us will protection to get to our win con. Most conveniently we have out tutors such as Solve the Equation and Fabricate among a few others. We can also use some other things like Urza's Saga to tutor a critical artifact, Expedition Map to pull out a Glacial Chasm to prolong the game, and Training Grounds to primarily abuse Kefnet's mana sink but can also be part of a combo later on.
At this point we are trying to piece cards together in order to build an infinite blue mana combo. Below is a list of all the ways I know how to make this happen as of the time of this writing:
Have Displacer Kitten on the battlefield and cast ideally Mox Amber for infinite blue but can also be done with Sol Ring and Mana Crypt for infinite colorless mana. If you are using the later, you can always filter it through Prismite or Stonework Packbeast.
You can Empowered Autogenerator on the battlefield along with Voltaic Key and Rings of Brighthearth. When you tap Empowered Autogenerator it will create X blue mana which can be dumped into the later two pieces. Voltaic Key will untap Empowered Autogenerator and Rings of Brighthearth will copy the ability allowing you to untap Voltaic Key. You need at least three counters on the mana rock but it can potentially go off faster depening on what other mana rocks and lands you have out.
Have Empowered Autogenerator tapping for at least three mana along with Filigree Sages which can untap it or you can have it go off faster with Training Grounds out.
Finally you can go down an interesting road of casting High Tide to make all your lands tap for two mana a piece, then cast Scholar of the Ages to bounce back High Tide and whatever else you want. Cast a bounce spell such as Snap to return Scholar of the Ages to your hand and untapping two lands. Then repeat the process to make all your lands tap for absurd amounts of mana.
Now the moment you've been waiting for. You need Mana Crypt in play as well as Scholar of the Ages, Stolen Identity or Echo Storm, and Ghostly Flicker in hand. Cast Stolen Identity targeting Mana Crypt, now you have two of the rocks. Play Ghostly Flicker targeting Scholar of the Ages allowing you to return Stolen Identity and Ghostly Flicker back to your hand. Repeat this process for infinite Mana Crypts. Then you are going to do the same wheel of interaction again but swap out Stolen Identity with Donate so that you can give all the Mana Crypts to your opponents. As soon as you are ready, simply say pass; you are also ready when you have a number of counter spells in hand in cast someone has something like a Vandalblast or Cyclonic Rift up their sleeves.