Concept - Every time your opponent casts a spell they will pay for it with their life.
Taking all of the fun Red and R/X cards that ping your opponents when they play spells, or even making them pay when they don't.
THE LOW END
Lightning Bolt - Fairly self explanatory, but it's going to be on you to judge whether you slam it to their face early or save it for removal.
Ash Zealot - 2/2 Haste w/ First Strike is already good. This little lady also jams up flashback and black decks looking to cast from the graveyard.
Eidolon of the Great Revel - You've already made your cast back if they spend a removal spell to kill him. He can hurt, especially if you get multiple out, but it will almost always hurt them more since you are playing hastey aggro.
Boros Reckoner - They get hurt if they put anything in front of him or target him with burn. Not a direct 'pay to play' like most of the deck, but definitely jams up your opponent on the ground.
Scab-Clan Berserker
- People are focusing on Abbot of Keral Keep as the red break-out card from Magic Origins, but I like Scab-Clan a lot better. 2/2 with Haste, grows into a 3/3 that then pings for 2 on every non-creature cast. Slam it turn three after casting a turn two Eidolon and that's 4 damage per non-creature.
MID RANGE
Huntmaster of the Fells
- While he has a tendency to get picked off fast by removal, even just 4 power and toughness over two bodies is a decent start. Having Flip werewolves makes things a little tricky in deciding what to play when, but you can also abuse it.
Mondronen Shaman
- The other Flip creature, this one needs to flip to be worth it but if she gets there it's really worth it. 3/2 becomes a 5/5 that pings 2 on every opponent spellcast.
Balefire Liege - Now, this guy might not play into the 'pay to play' mentality of the rest of the deck, but he does combo nicely since all of you other creatures are red or red/x. He is especially nice with a Reckoner on board, turning the minotaur into a 5/5. He still pings though, doing 3 damage on your red casts. Late game Lightning Bolt? That's 6 damage not 3.
ENDGAME
Dragonlord Kolaghan - 6/5 Flying Haste, he's the only creature with a way to avoid blockers on the ground so is already real nice, as is giving your other creatures (those that don't already have it) haste. The really big thing though is blocking duplicate creature spells from the opponents graveyard. 10 Damage is massive!
Ruric Thar, the Unbowed - 6/6, Vigilance, Reach, Attack each turn if able. More importantly, whenever a player plays a non-creature spell they take 6 damage. WARNING: This one hits you too! Thankfully you're only playing 4 non-creature spells before sideboard.
Kaervek the Merciless - 7 mana is a lot for a 5/4, and I'm still on the fence about him, but his ability to deal the CMC of every spell your opponent casts to them seems real good. Only a one-of due to cost, he's also side-out material.
SIDEBOARD
Blasphemous Act - I've found in testing one of the big weaknesses of the main board is facing down other creature-heavy decks. This bad boy certainly has an answer for those, and casts cheaply too. Play it with a Reckoner on the field and you can bounce that 13 damage straight to the opponent as well.
Blood Moon - For anything that isn't running primarily red. It CAN screw with you too, so make sure early you are searching for your basic forest/swamp if you can.
Burning-Tree Shaman
- To combat ability decks like Twin and Affinity
Grafdigger's Cage - A beauty to shut down decks that want to pull shenanigans with recursion and pulling out of the deck. I'm looking at you Goryo's Vengeance and Collected Company. Suggested by MadStacks.
Mindsparker
- Self explanatory, the first strike is added goodness.
Shatterstorm - I have a bunch of artifact decks (affinity and combos) in my local meta so an artifact-wrath is helpful.
I'm always open to suggestions, but I am CURRENTLY SEEKING: Something to combat Amulet Bloom (as there is one in my local scene) and Infect as well any thoughts on other major meta matchups.