Mono Red Madness wants to race with cheap burn and Guttersnipe/Kessig Flamebreather triggers, so cheap interaction and incidental lifegain matter more than slow value plays. Tragic Slip is efficient, cheap removal for their 1/1s (Voldaren Epicure) even without morbid, and can also finish off Guttersnipe or Kessig Flamebreather's 1/3 body once morbid is active. Sylvok Lifestaff buys life against the burn plan when equipped to any creature that's likely to die anyway, which is constant in this deck. Sadistic Glee is too slow and doesn't affect the race, and Accursed Marauder is a low-impact body against a deck that doesn't mind sacrificing a small creature. Keep the low curve and sacrifice synergies intact since this is fundamentally a race you win by grinding value and gaining life.

Dimir Control leans on countermagic and card selection rather than a wide board, so Mesmeric Fiend is excellent here, proactively stripping a Counterspell, Cast Down, or Gurmag Angler before they can use it, and its ETB dodges Spell Pierce entirely. Tragic Slip is efficient, cheap removal that answers their Faerie Seer and Spellstutter Sprite for a single black mana, and Morbid is easy to enable in our sacrifice-heavy deck to take down Augur of Bolas. Rite of Consumption and Sadistic Glee are both too slow and reactive against a deck that will simply counter or remove our payoff pieces, and Unearth's best reanimation targets get devalued when Cast Down and other removal are already plentiful in their maindeck. This leaves our core sacrifice engine (Carrion Feeder, Bloodthrone Vampire, Nested Shambler, etc.) fully intact while adding proactive disruption and clean removal against their sea of small blue creatures.

Affinity floods the board with cheap creatures (Refurbished Familiar, Glint Hawk, Kor Skyfisher) and recurs creatures with Blood Fountain, so graveyard hate has real upside. Faerie Macabre and Nihil Spellbomb can exile creature cards from their graveyard, denying Blood Fountain's recursion value, while Faerie Macabre also blocks their small fliers. Accursed Marauder is weak since Affinity has plenty of expendable small creatures to sacrifice instead of a real threat. Sadistic Glee is too slow against a deck that curves out with 2/2s and 2/1s, so it's cut in favor of more proactive, cheap disruption.