Standard Grixis Control

Creatures [8]:
4 Augur of Bolas
2 Snapcaster Mage
2 Olivia Voldaren

Sorceries [7]:
2 Dreadbore
2 Mizzium Mortars
3 Rakdos's Return

Instants [13]:
3 Devour Flesh
3 Desperate Ravings
3 Izzet Charm
2 Thoughtflare
2 Magmaquake

Planeswalkers [5]:
3 Liliana of the Veil
1 Tamiyo, the Moon Sage
1 Nicol Bolas, Planeswalker

Lands [27]:
4 Watery Grave
4 Dragonskull Summit
3 Blood Crypt
3 Steam Vents
3 Nephalia Drownyard
4 Drowned Catacomb
4 Sulfur Falls
2 Swamp

Sideboard:
1 Magmaquake
2 Tribute to Hunger
2 Witchbane Orb
2 Psychic Strike
1 Counterflux
1 Psychic Spiral
2 Tragic Slip
2 Pillar of Flame

Been messing around with this deck for ages now, trying to make it work in the current meta, given control decks tend to need blue and white for Sphinx's Revelation, since Grixis is by far my favourite 3-colour combination.

Counter magic's gone from the main entirely now due to the huge amount of heavy aggro lists, the constant presence of Cavern even if its numbers have dropped, and the fact that the best counterspells can often be somewhat tough on the mana (I've stopped liking maindecked Psychic Strike in a deck where mill is not the main win condition) especially with Liliana in the deck and wanting to hit Mortars overload mana (albeit the latter isn't a huge deterrent).

Magmaquake is a card I've seen discussed quite a bit in the MTGS thread, and it seems fantastic here, especially since if it'd kill one of my Walkers, I probably don't need to use it. The fact that it fireballs Jaces, Tamiyos, Lilianas, Garruks and even Domri Rades makes it absolutely fantastic. Similarly, with Dreadbore, the deck's flexibility really makes me like it over other more streamlined decks like Esper (in the sense of how the deck plays and its main focus).

Thoughtflare and Rakdos's Return are the deck's Sphinx's Revelations. Thoughtflare does all the digging necessary without having a weak mid-game like Sphinx's Revelation does, and Rakdos's Return just wins any non-aggro matchup by itself.

The sideboard is still pretty rough, I find myself changing cards virtually every day, any suggestions for that are also welcome.

Have at it.

20 spells is on the low side for my personal tastes. I consider about 22-23 the ideal amount. I don't know about 3 Rakdos's Return. I'd rather play Cyclonic Rift or Searing Spear over one of them.

20 spells is fine for Augurs, and Snapcasters, and other than those two, Planeswalkers are essentially spells too, making for 25, in a sense. Heck, all things considered, Olivia's the only non-spell in the deck, essentially.

3 Rakdos's Returns takes multiple things into account:

1. It wins games literally by itself, and it's good against everything except very fast aggro decks, which the rest of the deck can quite easily deal with.
2. It can easily be discarded early on with Izzet Charms, Thoughtflares and through Liliana, the deck has tons of card filtering.
3. I don't want my "best spell" vs control to be gone for good from an unlucky Desperate Ravings.

Searing Spear seems incredibly weak by comparison.

Cyclonic Rift seems nice in theory, and I have tested it a lot, but it's too often just a Disperse, especially since it doesn't exactly scale the way Rakdos's Return does, and if they have enough permanents to make it not a really bad 7 mana double-disperse then I'm already dead since I've either drawn lands and no spells, or spells and no lands. This deck keeps board presence to a complete minimum.