Arcbound Slasher - Seems good in a deck full or artifact creatures, otherwise not really. 5 mana is a bit prohibitive, but being able to recoup your losses when this dies more than makes up for it. The riot fits this card well mechanically but not thematically. Boarderline, (cubeable with a good amount of artifact creatures).
Arcbound Tracker - Less exciting of a modular creature than Arcbound Slasher. This plays into the sets mechanics well intersecting between storm and artifact creatures. As a pauper card it is well below curve with no synergy, and is only ok with lots of artifacts. The storm is hard to pull off in pauper singleton, and I doubt this is on of the the pay-offs you'd play in that case anyway. Sort of similar to Spellgorger Weird, but I like the weird more since it is more consistent. Menace means this is a problem creature if it ever gets big. Borderline (mostly because of synergies).
Battle Plan - Expensive for what it does. Sort of acts as a overpriced equipment that you don't have to pay for once it gets going, the real downside is it is power only and only activates during your turn. 4 mana is a lot. Bad to borderline. (It's not that bad but it isn't good either.)
Faithless Salvaging - I feel like this card was costed at 1 mana, but ended up being way too good, and now is basically mediocre except as a madness enabler. Bad, (cubeable with madness, because then it is an enabler and a card filter).
Galvanic Relay - Very good storm payoff. Problem is storm is lacking sufficient singleton support, and storm doesn't have cross synergies with other strategies. Bad all the way to staple, really depends on whether you enforce the singleton rule or not to support storm.
Gargadon - Sort of a red Errant Ephemeron. Flying is a bit better than the extra power/toughness and trample, but in saying that, this looks good. Very good in fact. It's going to hit hard, or at the very least demand and answer (preferably at instant speed). Not bad for 2 mana and 4 turns. Cubeable, (potential to be upgraded to staple, but let's not be too hasty).
Gouged Zealot - There have been a string of 4 mana value 4/3's in red recently and this is the best of the lot. Reach is a nice keyword to have, though it does nothing on offence. Much better than Flummoxed Cyclops since Gouged Zealot actually knows how to block. I guess its time to talk about delirium. It's a whatever mechanic for pauper cube. There simply isn't much in the way of card hitting the graveyard that aren't creatures, instants or sorceries. The upside of this card's delirium isn't insignificant either, just a cheeky 1 damage to each creature defending player controls isn't nothing to sneeze at. But realistically this card alone isn't worth warping deck-building for. Borderline, (would be cubable if delirium was more reliable).
Lightning Spear - Basically an over-costed Lightning Strike/Searing Spear with a bad equipment attached. (hey, it gives trample.) Bad to Borderline. (Really need a more fine grained rating system.)
Mine Collapse - If 5 damage was a premium for removal this would see more play. Good at killing Imperiosaurs, but there isn't much that a Flame Slash can't already kill, so it doesn't really justify the four mana price tag (or 1 mountain). Plus is can't deal damage to players which is kind of red's whole thing. Cubeable (more of a red control card).
Mount Velus Manticore - This is one of the most Modern Horizons 2-esque cards. Not keyword jamming this time, instead finds as much overlap is archetypes as possible. Borderline (it's only an ok madness enabler.)
Revolutionist - Hey, it's Anarchist! I mean red Archaeomancer. Without madness this is a little bit on the expensive side for that ability. Another version of this helps for setting up Ephemerate loops. With madness this is well costed and can be used to recoup losses from earlier discards by accruing card advantage. Borderline, (Cubeable with madness).
Skophos Reaver This card is good even without madness. Basically a Brazen Wolves reprint, but with upside. Staple (it's strictly better than a card already found in most red sections).
Viashino Lashclaw - I get it, it enables madness (and I guess delirium). Bad to borderline (can't bring myself to call a 2/2 for 2 with upside bad), (cubeable with madness).
Overall: Madness cards are fine and there are more madness enablers. Skophos Reaver is very good. Gargadon is pretty decent. There are lots mechanic mashups and in-jokes in this section.
Red
Arcbound Slasher - Seems good in a deck full or artifact creatures, otherwise not really. 5 mana is a bit prohibitive, but being able to recoup your losses when this dies more than makes up for it. The riot fits this card well mechanically but not thematically. Boarderline, (cubeable with a good amount of artifact creatures).
Arcbound Tracker - Less exciting of a modular creature than Arcbound Slasher. This plays into the sets mechanics well intersecting between storm and artifact creatures. As a pauper card it is well below curve with no synergy, and is only ok with lots of artifacts. The storm is hard to pull off in pauper singleton, and I doubt this is on of the the pay-offs you'd play in that case anyway. Sort of similar to Spellgorger Weird, but I like the weird more since it is more consistent. Menace means this is a problem creature if it ever gets big. Borderline (mostly because of synergies).
Battle Plan - Expensive for what it does. Sort of acts as a overpriced equipment that you don't have to pay for once it gets going, the real downside is it is power only and only activates during your turn. 4 mana is a lot. Bad to borderline. (It's not that bad but it isn't good either.)
Faithless Salvaging - I feel like this card was costed at 1 mana, but ended up being way too good, and now is basically mediocre except as a madness enabler. Bad, (cubeable with madness, because then it is an enabler and a card filter).
Galvanic Relay - Very good storm payoff. Problem is storm is lacking sufficient singleton support, and storm doesn't have cross synergies with other strategies. Bad all the way to staple, really depends on whether you enforce the singleton rule or not to support storm.
Gargadon - Sort of a red Errant Ephemeron. Flying is a bit better than the extra power/toughness and trample, but in saying that, this looks good. Very good in fact. It's going to hit hard, or at the very least demand and answer (preferably at instant speed). Not bad for 2 mana and 4 turns. Cubeable, (potential to be upgraded to staple, but let's not be too hasty).
Gouged Zealot - There have been a string of 4 mana value 4/3's in red recently and this is the best of the lot. Reach is a nice keyword to have, though it does nothing on offence. Much better than Flummoxed Cyclops since Gouged Zealot actually knows how to block. I guess its time to talk about delirium. It's a whatever mechanic for pauper cube. There simply isn't much in the way of card hitting the graveyard that aren't creatures, instants or sorceries. The upside of this card's delirium isn't insignificant either, just a cheeky 1 damage to each creature defending player controls isn't nothing to sneeze at. But realistically this card alone isn't worth warping deck-building for. Borderline, (would be cubable if delirium was more reliable).
Lightning Spear - Basically an over-costed Lightning Strike/Searing Spear with a bad equipment attached. (hey, it gives trample.) Bad to Borderline. (Really need a more fine grained rating system.)
Mine Collapse - If 5 damage was a premium for removal this would see more play. Good at killing Imperiosaurs, but there isn't much that a Flame Slash can't already kill, so it doesn't really justify the four mana price tag (or 1 mountain). Plus is can't deal damage to players which is kind of red's whole thing. Cubeable (more of a red control card).
Mount Velus Manticore - This is one of the most Modern Horizons 2-esque cards. Not keyword jamming this time, instead finds as much overlap is archetypes as possible. Borderline (it's only an ok madness enabler.)
Revolutionist - Hey, it's Anarchist! I mean red Archaeomancer. Without madness this is a little bit on the expensive side for that ability. Another version of this helps for setting up Ephemerate loops. With madness this is well costed and can be used to recoup losses from earlier discards by accruing card advantage. Borderline, (Cubeable with madness).
Skophos Reaver This card is good even without madness. Basically a Brazen Wolves reprint, but with upside. Staple (it's strictly better than a card already found in most red sections).
Tavern Scoundrel - What. A. Joker. Bad.
Unholy Heat - Sure, delirium. Cubeable (but nothing special).
Viashino Lashclaw - I get it, it enables madness (and I guess delirium). Bad to borderline (can't bring myself to call a 2/2 for 2 with upside bad), (cubeable with madness).
Overall: Madness cards are fine and there are more madness enablers. Skophos Reaver is very good. Gargadon is pretty decent. There are lots mechanic mashups and in-jokes in this section.