Updated list incorporating some of the more well-known and well-tested cards for the deck strategy drawing inspiration from the legacy mono-red or gruul variations, but without cards like Basking Rootwalla, so I had to get creative.
This deck got a lot of upgrades from Modern Horizons 2 especially with Blazing Rootwalla having a free madness cost, Rakdos Headliner not only facilitating discard but cracking in for 3 damage a turn, Kitchen Imp being a nice one mana haste 2/2, and lastly bone shard being a decent one mana removal sorcery.
Small Pox was replaced with Mind Rake which when not overloaded acts as an expensive Mind Wrench though it does have the option of being overloaded for a wheeling discard to benefit you and hurt your opponent.
Bone Shards uses discard to cheaply destroy opponents creatures, though it has an alternate cost in case you're met with a bind and no cards in hand with a creature to sacrifice.
Insolent Neonate gives the opportunity for a free discard and draw, is a 1/1 body until you use it for discard and only has 1 CMC so it probably takes the cake for the hand smoothing/cantrip slot, along with Seasoned Pyromancer and potentially Burning Inquiry card draw tends to stay smooth.
Liliana of the Veil serves incredibly well to cause your opponents to discard and facilitates your own discard strategies. Liliana of the Veil is a great way to wheel discard through to your opponent and when played on curve is a great way to keep your strategies rolling. Her being $80+ means three copies runs over $240 so a cheaper alternative option is Liliana, Waker of the Dead at around $4. She costs one more generic mana, but has a better plus one. Her minus is not a sacrifice effect so it could potentially be worse in the long run though it does allow you to target your removal. I also authored a budget version of the deck featuring this swap and more that can be found on my profile :)
There might be too much removal especially for the format where the average number of removal spells is somewhere around five. The three Bone Shards, the three Fiery Temper, four Collective Brutality and the four Liliana of the Veil being able to all remove creatures is a little heavy, although each of these cards have dual uses, but bone shards needs a target in order to resolve which restricts its second use, making it potentially mostly discard fodder.
The Rack shows up in the sideboard especially if the opponent is keen on spell slinging and ends up reducing their own hand size.
Liliana of the veil, although a value engine does fall victim to the legend rule so four copies is a little ambitious and seasoned pyromancer being another three-mana, value engine that helps you to draw cards is more deserving of four copies.
Vengevine is a maybe as a way to keep the creatures flowing and as an additional benefit to discarding, But currently Hollow One is a great way to gain advantage from discarding as it can be cost for either 0 or 1 mana from most wheeling discard.
Bloodghast and Flamewake Phoenix work beautifully with Bone Shards with either being discarded to it or sacrificed to it and still being able to be brought back with haste under their respective constraints.
