Oh, I was hoping this day would never come. This conversation is horrifically awkward.
Well, here it goes.
Sometimes, when a mommy Zoo deck and a daddy Abzan deck love each other very much, they want to...express that love...in a...physical...manner. And sometimes, when they...do that… they make a baby.
All that stuff about cabbage patches and storks we told you when you were younger wasn't exactly how it happens. In reality the mommy Zoo deck carries the baby in her stomach for about nine months, and once the baby deck is big enough, mommy and daddy go to the hospital and the baby is born.
The baby is half its mother and half its father, but as a whole is something a little different. It still wants to use early discard to clear the path for a powerful two-drop and disrupt opposing combo decks, but now it can be even more aggressive with Wild Nacatl, and rather than draw a lot of extra cards, it uses Grim Flayer and Lingering Souls to generate advantage while also applying a lot of pressure like a Zoo deck.
And it still plays a lot of removal like an Abzan deck or its cousin Jund does, but most of that removal is damage-based, so you can use it as reach as well as removal. Tribal Flames is particularly good at this, leveraging your painful manabase to become a four- or five-damage spell that will close games in a hurry.
The result is a deck that isn't quite aggro and isn't quite Rock; it's aggro-Rock. Before you were born, Rock decks were popular in Extended, using Troll Ascetic and Umezawa's Jitte to pressure control and combo decks in a way that can interact profitably with aggressive decks. This Modern incarnation of the deck is more burn-heavy, but that's to be expected when its creatures are so much more efficient. Modern is a fast format, and the ability to overload on removal spells without risking drawing too much air in a non-interactive race is very important.
Lingering Souls is honestly out of place in the scope of this deck, but the synergy with Grim Flayer is likely too good to ignore and the Spirit tokens can peck away at a control opponent's life total to put them into burn range, so I imagine they earn their place, even if they aren't the best aggressive choice in a vacuum.
And I think that's about it. Do you have any questions?
Nope. All right, then. Just be safe out there, okay?