Do you get eventually bored of playing the same deck over and over? Worry no more! Bolas and his chaps got you covered. This is the deck that will give you more bang for your buck, by offering more replayability than any other, by playing the opponent's cards against them.
It starts the early game with a typical grixis control build, using discard, counter and removal spells like Fatal Push, Inquisition of Kozilek (i choose it over thoughtseize because this deck's manabase is already heavy enough on self damage), Mana Leak, Countersquall and Lightning Bolt.
Echoing Truth against tokens and enchantments, which grixis has no way to destroy.
On T2 you can play Kitesail Freebooter following along the hand-control plan, which gives you a pseudo-discard while gathering intel about the opponent's hand. It tends to attract some hate, which can come handy on the first match, as it acts as a lightning rod to clear the path for your T3 Thief of Sanity.
If it survives until T4, it can help you sneak a Fallen Shinobi for a free hit and some free spells!
T3:
Thief of Sanity: The art! The flavor! It looks like a freaking nazgul scouting ravnica for the Invisible Stalker wearing the Sol Ring. It is the deck's main generator of card advantage and replayability. Since we are talking about modern, most spells should be cheap to play. Also, it can serve the purpose of eliminating important combo pieces. Finally, it's also a good target for Fallen Shinobi.
Bedevil and Kolaghan's Command as a catch all (except enchantments) answer to anything.
T4:
Fallen Shinobi: God do I love this card. It is complemented with the rest of the crew so well. Since almost all your other creatures have flying, the probability of them being left unblocked is substantial. Thus, you can easily sneak a Ninjutsu on your enemy, hitting for 5 and casting 2 free spells.
Moreover, by returning your creatures to your hand, you can reutilize their ETB effects, like the discard from Nicol Bolas, the Ravager
or the exile from Kitesail Freebooter.
Nicol Nolas, the ravager has a discard ETB effect, and poses a great menace in the air. If you get to transform it, you can reanimate the opponent's dead creatures and planeswalkers.
T5:
Nicol Bolas, Dragon-God steals your opponent's planeswalker's abilities, while generating card advantage and being a wincon on its own.
The Scarab God: Resilient threat that lets you copy the opponent's dead creatures, or bring back your usually feeble Kitesail Freebooter and Thief of Sanity as 4/4 flyers, which is nothing to scoff at.
T6:
Dragonlord Silumgar dives in to steal their already ticked up planeswalker or finishing creature to close the game.
Alternatively, a Dragonlord Kolaghan is also a great finisher that plays along the line of this deck. With so much removal, a soft lock is guaranteed when he hits the board.
