I have been trying to put together an Elder Mastery deck for quite some time now and after quite a bit of testing, this is what I have come up with. I will admit that the card is a little overpriced (really wish it cost one less mana), but it is really fun when it works. This deck is not easy to play and requires some really careful decision making and planning. About card selections:
Guttersnipe: The MVP of this deck by a long shot. Once you get Mastery on it it is usually game over. Playing without it out there is still usually really powerful for chipping away at opponent and making them change focus to removal rather than casting powerful creatures, plus it is hilarious making an opponent discard 2 cards on a counter-spells once you do have Master out there. Very thematic to Grixis in my book.
Sparkmage: Can ping opponent to death or deal automatic damage for Mastery. Feel like this card is so underrated. I usually don't cast the little bastard until I have Elder Mastery ready to go but sometimes I make exceptions if I feel like I can counter enough to not lose him automatically.
Shock, Anger of the Gods, Auger Spree: much needed removal for deck. Hopefully counter-spells are enough to keep opponents off the board.
Negate, Nullify, Dissolve, Traumatic Visions: Counter, Counter, Counter... but be careful what you choose to counter too. Traumatic Visions also helps with some mana fixing.
Tribute to Hunger: Because there is usually only singletons out because of all the countering, this card can be really good at times.Think Twice: Keep the draw engine going and hopefully draw into one of the three Mastery before it is too late.
Inferno Titan: Didn't want to include at first but is just too powerful in any deck that has red in it.
Charmbreaker Devils: Can be really powerful with all the spell casting and obvious semi-tutoring can be really good (and lucky).
The deck runs very much like a lot of the Izzet decks out there but hopefully still does Lord Bolas proud. As always, I really appreciate any feedback on this and hopefully you enjoy as much as I have!
Edit 1: Went w/ Hakeem's suggestions and replaced Tribute to Hunger with another Charbreaker Devils and a full set of Auger Sprees. Also replaced one Negate and Nullify with two Traumatic Visions. Haven't seen much of a difference yet, but am hopeful.