Just saying, you have no lands.

Lands now added. I didn't have them in originally as I was just focused on making cuts.

You could run Time Stretch for just those great extra turns. +1 great deck

Plus Omniscience

I think you would like some of black's best removal/control spells, Tragic Slip and Sudden Spoiling.

Have you considered Torrential Gearhulk ? You can use it and other cards like it to recast an instant from your graveyard, which can reduce the amount of instants you need.

For mana ramp, I see you have Sol Ring and some fetch cards, but consider using Opaline Unicorn, Manalith, Prophetic Prism, and Cultivator's Caravan. You can reduce both your fetch cards and some land cards with the con of having removable permanents. With the same mana idea in mind, other great cards for coloured mana are Elvish Mystic, Arbor Elf, Satyr Hedonist, Voyaging Satyr, Zhur-Taa Druid, Cabal Coffers, and other cards along those lines.

Great looking deck regardless of anything I've said. I actually had a hard time coming up with suggestions.

Also, I see you don't have an Evolving Wilds. I'd substitute this for a fetch land if you can because it costs nothing to cast, can't be countered, and can act as a land if you don't have any basics left in your library.