Alright, so I spent some time thinking about this deck and especially about how to make Approach of the Second Sun actually work and be viable in a standard deck. This is the solution that I came up with.
So basically you have three or four wincon in the deck, ideally you have at least one for each color. Naturally you can win by playing two Approach of the Second Sun, if everything goes according to plan it should go back in seventh position in your library, then all you have to do is cycle your cards until you get it again, Negate is here just to make sure that the second Approach of the Second Sun is not getting countered. If you manage to play Archfiend of Ifnir and keep it long enough on the field, you've basically won the game against any creature based deck since all you need to do is cycle enough cards to either kill or make your opponents monsters useless, here again, Negate is here to ensure that your main threat stays on the field. Play Drake Haven as soon as you can if need be, it'll allow you to generate 2/2 flying tokens which really gives more durability in the long game, and if you've managed to keep your oponent docile enough, you can even win by swarming them with an army of flying drakes. Now you may consider As Foretold and New Perspectives as wincon since once they are in play they make your game that much faster and much more reliable by allowing you to cast spells and to cycle for free which is, shall I remind you, what you're gonna be doing most of the game since the whole deck was built around that mechanic.
Other than that you have cards that allow you to sustain some durability like Murder which just works a charm if you manage to get the two black manas required (which isn't that much of a problem when you can cycle most of your deck) or you could just swich some of your Negate for some Essence Scatter but, really, Archfiend of Ifnir should already do a pretty good job on his own. Curator of Mysteries allows you to scry when you cycle (aside frome being a solid 4/4 flying for 4 mana) which can let you choose for which card you cycle or just get rid of one more card that separates you from your second Approach of the Second Sun, oh and just in case, it cycles for one mana so that also makes him a very solid card in this deck. As Foretold fulfills two roles, many cards in this deck are pretty expensive so it allows you to play your spells a bit more easily by removing the cost of one of your spells each turn (including the ones of your opponent) and it also allows you to freely cast a Negate or a Dispel to protect your big threats that wouldn't leave you enough mana to do so otherwise. Also, remember that time you were going like: "Oh, man ! I wish I had more cards to cycle in my hand right now, I've cycled, like, twice the size of my hand !", well worry not, Shadow of the Grave is gonna give you plenty of that, in fact, double that actually so just use it whenever you would need to cycle a little more or keep some under your hand or even prepare a big turn with the effect of New Perspectives.
