This is the most recent combo to grace the cube. As with most combo decks this has strengths and weaknesses. The strengths are that there is a decent amount of redundancy for most of the pieces you want, it is very quick and fairly reliable. The downsides of the deck are that you need pretty much all the green mana dorks which can tap to produce multiple colours, you need a really good four colour mana base that can play green spells turns one and/or two and still cast an Ascendancy on turn three, and lastly you have only one Ascendancy, should it be dealt with your deck does nothing! You can also be disrupted on the Ascendancy side like a combo deck or the creature side like more normal decks. A red burn deck has nothing against enchantments and rather than play extreme solutions it can just play cheap instant burn. Sylvan Caryatid is great for getting the ball rolling safely against removal but you always need more than that if just for the ability to attack with it!
The plan is fairly simple, have at least one active mana producing critter in play and make an Ascendancy. At that point basically every spell in your deck either produces mana or is mana neutral and typically is also draw two, discard one. You can rapidly draw your whole deck once in this position. Before near decking yourself it is wise to spend any spare mana you may generate on making further mana producing critters and use one of the haste spells to turn it on. At this stage every spell in the deck generates mana. You carry on doing this cast, pump, untap and bonus loot routine until you have enough damage to kill in one swing.
As this list is all so focused around the one effect there isn't room to go cramming extra combos in which is reasonably unusual for cube. Even the engine combo decks in cube tend to have sufficient overlap or utility from other combos in the cube to double up. There is also an argument to go black for the extra tutors because the deck is so reliant on having the Ascendancy. Black also lets you proactively take away their disruption for the Ascendancy and a 5th colour is not quite so hard when you are already packing lands that tap for all the colours. Deathrite Shaman is interesting in the list as it allows you to partially go off with him as a mana source but also exile lands so that reshuffling graveyards is even better. Treasure Cruise is another top rate card that helps remove unwanted graveyard cards prior to a reshuffle.
Birds of Paradise
Slight of Hand
Path to Exile
Visions of Beyond
Fire / Ice
City of Brass
As part of your combo is having cheap spells to untap your stuff you are able to play a couple of useful utility spells which can be bounce, recursion, burn, removal, or countermagic etc. This list is greedy and even runs a Fire / Ice but at least it can draw. You don't want too many spells that don't draw cards as you will run out of gas when going off. The Gaea's Blessing allows you to go off forever, only if you get something exiled is it then a problem, Blessing can get things you need back but it is rather slow and clunky, Noxious Revival is a much more direct tool that is best at undoing things like Negate or Duress hitting you at a bad time. It is also handy as it doubles up as a mana producer when you are going off.
Spellskite is a card that in no way helps with the combo (I guess that isn't totally true as it can be part of the attack squad) however it protects you and usually all the different parts of your combo as well. Given that those are the decks main weakness I think this is a worthy inclusion. Modern versions of the deck run Glittering Wish and the 4th Ascendancy in the board giving them great security on that front. Glittering Wish is a consideration for this list in appropriate cube formats as you can get some really powerful gold cards when you are 4/5 colours and you can still have a fighting chance of winning should your Ascendancy somehow get exiled.
Fate Stitcher is a cute addition to the list acting as one of the best mana producers in the deck, you only need it for one turn and so the unearth is incredibly powerful. It is essentially a Birds with haste and draw a card once you get going. The Retraction Helix is another cute addition allowing you to do several things. Either you can just stick it on a spare dork and clear their board of blockers and problem cards before your fatal swing or you can use it and two dorks (one of which can tap to produce blue mana) to loop untaps and pumps without needing you use your library several times over. Without the Helix this list would need more draw effects like Serum Visions and Treasure Cruise and less things like Path and Spellskite, you have way too high a chance of fizzling before you have fatal attacks in this list without it. In many ways Retraction Helix is the Upheval of this list compared to artifact based decks.
The deck is much better than its performance and levels of play would suggest. This is because the formats in cube where you have access to all the niche cards are also the ones which getting all the premium green mana dorks and all the premium lands is really hard and rare. On top of this those formats are also the ones which people are able to counter draft to your plan. Suddenly you find yourself up against Erase and Transgress the Mind and your expected win rates plummet. This deck is obviously best with an optimal mana base (which isn't miles of the one I suggested) however it is totally workable with weaker lands, likely it makes Arbor Elf unplayable which is a shame but not too damaging. Things like Vivid lands are fine if that is what you need.
What I like most about this deck is that you get to use loads of cards everyone has to read! It is always good to have something fresh and different at the table and this is very much both of those things. It may not be tier one but it is certainly competitive and makes up for much lost ground by being unfamiliar and therefor much harder to play against.