Nexus of Fate gives a blue deck another turn at instant speed. Seven mana is expensive, but the timing lets you wait through opponents' decisions before committing. Casting it near the end of a turn can set up an untap, a draw, and another full opportunity to use the board you already control.
Its replacement effect shuffles it into its owner's library instead of letting it enter a graveyard from anywhere. That applies after resolution, when it is discarded or milled, and in many situations where it is countered. It does not make the spell uncounterable, and effects that exile it can prevent the normal reshuffle route.
Decks with strong card selection can find Nexus again over time, particularly as the library becomes smaller. The reshuffle alone does not guarantee an immediate loop; you still need a way to locate and cast it repeatedly. Ordinary graveyard spell recursion is not the natural plan because the card usually does not remain there. Extra turns become more useful when you have planeswalkers to activate, attackers ready to connect, or engines that reward untapping and drawing. On an empty board, seven mana may buy little more than another chance to develop. Use the instant timing to preserve options, then commit when the next turn will produce a meaningful advantage. Nexus works best as part of a deck already able to generate and spend substantial mana while maintaining useful actions across repeated turns.
