Doom Whisperer + The Gitrog Monster will make a janky ass but super fun combo deck. Basically mill your entire library, using Nourishing Shoal on Worldspine Wurms to replenish your life (and leaving the unnecessary ones to prevent milling yourself), and you win by... get back to you on that one later.
I like how this Lazav can copy your stuff. Makes him much easier to build around than the original. Now to find a Grixis commander suitable to play Lazav with Grenzo, Dungeon Warden.
Mad Rush, its iffy on whether this can be red, but the lose clause is way too easy making it far too strong. I feel this is strong, balanced design. Consider it a Relentless Assault that cantrips but requires you to empty your hand or lose the game.
Sulferize, 3cmc land destruction has been a no go for 10 years now. It's mostly a proof of concept. Ideally, it would cost 4 and have an additional upside, like allowing you to Memoricide the copies of that card as long as it's not a basic land or something.
Valkyrie's Summons, might be too cheap and the flavor is weird. Not granting flying or changing their types helps a lot. Probably should cost 1 or so more, when compared to something like Back from the Brink.
Immolation Brand, Spite of Mogis that starts at 1, hits walkers and is instant is way too strong. RR to keep as an instant. Yeah, possibly should be RR or 1R.
Spellplate Goblin, potentially taking them away isn't an excuse to give non red keywords. Red doesn't get indestructible or hexproof. I feel like the triggering of the removal – going all in on a turn – fits red so well it merits the piebreak.
Goblin Hoarder, peek at cards stashed??? Why peek? Stash overall seems like a bad keyword. It looks to far too easily let you loop back cards. Cause they are face-down, otherwise you wouldn't know what's in there.
Tibalt is way too good. I wouldn't be upset to see this exact card at 2RR, not quite happy but not upset. At 3cmc it shouldn't offer a choice on the looting and only add 1 when the devil dies. Would easily be the best red walker. Probs so, but the fact that the +1 doesn't generate card advantage of any kind makes me believe it might fly.
Works well in Standard with Traxos, Scourge of Kroog. Casting it untaps Traxos and allows you to surveil for more Historic permanents, while also being able to copy Traxos for a relatively small amount of mana.
Mad Rush I 2RR Sorcery
Take an extra turn after this one. At the beginning of that turn's end step, you lose the game unless you have no cards in your hand.
A variation on Final Fortune that favors all-out aggro.
Sulfurize I 1RR Sorcery
Destroy target colorless permanent.
Sidegrade to Pillage – hits Ulamog, doesn't hit Gearhulks.
Valkyrie's Summons I 4RR Enchantment
At the beginning of your combat step, you may exile a creature card in your graveyard. If you do, create a token that's a copy of it onto the battlefield tapped and attacking, except it's a red Phoenix and it gains flying.
Red rarely has card advantage, and this can give recursion while maintaining an aggressive flavor.
Immolating Brand I R Instant
Immolating Brand deals 1 damage to target creature or planeswalker.
Spell Mastery – If there are two or more instant and/or sorcery cards in your graveyard, Immolating Brand deals X damage to that target instead, where X is the amount of instant and/or sorcery cards in your graveyard.
Versatile Skred that has a more sensible build pattern for decks and allows Red to have an answer to, say, late-game Teferi.
Spellplate Goblin I 1RR Creature – Goblin Wizard
Indestructible, hexproof, menace
When an opponent casts their second spell each turn, Spellplate Goblin loses indestructible, hexproof and menace.
[3/1]
Red decks in general suffer vs. stompy match ups and fighting late-game value cards. Spellplate Goblin can slink past single fat blockers and avoid removal if the opponent is focused on using fat cards. If the opponent can string two spells together, however, they can value out this guy really hard. It's also a good tool for Goblin decks in general to tutor for.
Goblin Hoarder I 2R Creature – Goblin Rogue
Haste
When Goblin Hoarder enters the battlefield, each player stashes their graveyard. (To stash a card, exile it face-down and put it in your stash. You may peek at cards in your stash. Whenever a player would draw a card, they may put a card from the stash pile into their hand instead.)
[2/3]
Graveyard hate that's not quite graveyard hate. Let's you bring back value Goblins in Legacy play, even if it allows your enemy to recuperate by redrawing sweepers. With Haste, it can slide for a few hits before the enemy sweeps, and it's P/T makes it good to send into trades and it dodges Kolagan's Command.
Tibalt at Wit's End I RR Planeswalker
{+1} – Target player reveals a card at random from their hand. You may have that player discard that card. If you do, that player draws a card.
{-1} – Create a 2/1 red Devil token with haste. When it dies this turn, put 2 loyalty counters on Tibalt at Wit's End. At the beginning of the end step, exile this token.
{-6} – You get an emblem with "At the beginning of your end step, discard your hand and draw three cards. If you would draw a card while your library has no cards in it, you win the game instead."
[2]
A different kind of Red walker. +1 can lightly screw your opponent's plans, or perhaps give you a chance to filter some bad cards on your hand. -1 helps putting pressure on enemies, and allows you to punish blockers by having Tibalt gain loyalty out of the exchange plus opens up possibilities for burning out the blockers with the extra 2 points of damage. Ultimate accelerates your drawing power, and gives you an alternate win con. Best part about is that you can aggressively use Tibalt's +1 to get there faster!
Designer 1: Hey, remebmer Grim Haruspex?
Designer 2: No, I don't.
Designer 1: It's a cool nice card that impacted no formats whatsoever...
Designer 2: One minute... let me check gatherer... ok, found it, what about it?
Designer 1: I've made it WORSE and printed as rare!
Designer 2: You're the best designer ever!
Alternatively:
Designer 1: Hey, what's keeping Death Shadow from being a top tier deck?
Designer 2: It folds too quickly to Wrath effects.
Designer 1: What if there were a card that could be a decent beater, grew your Death Shadows, and helped you replenish your hand after Wrath effects?
I feel like she's meant for Legacy play, even if she's not the best of colors. She can filter your *****tier lands, and kill most Legacy permanents. Her +2 feeds Grumag Anglers and Tasigurs while providing you with new fuel.
Ain't immune to Dryad Militant.
Mairsil, the Pretender.
Replies in blue.
Sorcery
Take an extra turn after this one. At the beginning of that turn's end step, you lose the game unless you have no cards in your hand.
A variation on Final Fortune that favors all-out aggro.
Sulfurize I 1RR
Sorcery
Destroy target colorless permanent.
Sidegrade to Pillage – hits Ulamog, doesn't hit Gearhulks.
Valkyrie's Summons I 4RR
Enchantment
At the beginning of your combat step, you may exile a creature card in your graveyard. If you do, create a token that's a copy of it onto the battlefield tapped and attacking, except it's a red Phoenix and it gains flying.
Red rarely has card advantage, and this can give recursion while maintaining an aggressive flavor.
Immolating Brand I R
Instant
Immolating Brand deals 1 damage to target creature or planeswalker.
Spell Mastery – If there are two or more instant and/or sorcery cards in your graveyard, Immolating Brand deals X damage to that target instead, where X is the amount of instant and/or sorcery cards in your graveyard.
Versatile Skred that has a more sensible build pattern for decks and allows Red to have an answer to, say, late-game Teferi.
Spellplate Goblin I 1RR
Creature – Goblin Wizard
Indestructible, hexproof, menace
When an opponent casts their second spell each turn, Spellplate Goblin loses indestructible, hexproof and menace.
[3/1]
Red decks in general suffer vs. stompy match ups and fighting late-game value cards. Spellplate Goblin can slink past single fat blockers and avoid removal if the opponent is focused on using fat cards. If the opponent can string two spells together, however, they can value out this guy really hard. It's also a good tool for Goblin decks in general to tutor for.
Goblin Hoarder I 2R
Creature – Goblin Rogue
Haste
When Goblin Hoarder enters the battlefield, each player stashes their graveyard. (To stash a card, exile it face-down and put it in your stash. You may peek at cards in your stash. Whenever a player would draw a card, they may put a card from the stash pile into their hand instead.)
[2/3]
Graveyard hate that's not quite graveyard hate. Let's you bring back value Goblins in Legacy play, even if it allows your enemy to recuperate by redrawing sweepers. With Haste, it can slide for a few hits before the enemy sweeps, and it's P/T makes it good to send into trades and it dodges Kolagan's Command.
Tibalt at Wit's End I RR
Planeswalker
{+1} – Target player reveals a card at random from their hand. You may have that player discard that card. If you do, that player draws a card.
{-1} – Create a 2/1 red Devil token with haste. When it dies this turn, put 2 loyalty counters on Tibalt at Wit's End. At the beginning of the end step, exile this token.
{-6} – You get an emblem with "At the beginning of your end step, discard your hand and draw three cards. If you would draw a card while your library has no cards in it, you win the game instead."
[2]
A different kind of Red walker. +1 can lightly screw your opponent's plans, or perhaps give you a chance to filter some bad cards on your hand. -1 helps putting pressure on enemies, and allows you to punish blockers by having Tibalt gain loyalty out of the exchange plus opens up possibilities for burning out the blockers with the extra 2 points of damage. Ultimate accelerates your drawing power, and gives you an alternate win con. Best part about is that you can aggressively use Tibalt's +1 to get there faster!
Alternatively:
Designer 1: Hey, what's keeping Death Shadow from being a top tier deck?
Designer 2: It folds too quickly to Wrath effects.
Designer 1: What if there were a card that could be a decent beater, grew your Death Shadows, and helped you replenish your hand after Wrath effects?
This is a Zombie, bro. Much more relevant interactions.