38 cards where the card is available on Paper and it’s legal in Commander and the color identity ≤ BW and the text includes “as an additional cost to cast ~, sacrifice” and the mana value < 4

Altar's Reap (Commander Anthology #45)
Angelic Purge (Shadows over Innistrad #3)
Bankrupt in Blood (Ravnica Allegiance #62)
Bone Shards (Modern Horizons 2 #76)
Bone Splinters (Dominaria United #83)
Carrion (Mirage #111)
Corrupted Conviction (Outlaws of Thunder Junction #84)
Costly Plunder (Double Masters #80)
Culling the Weak (Exodus #55)
Deadly Dispute (Outlaws of Thunder Junction Commander #131)
Diabolic Intent (The Brothers' War #89)
Dusk Rose Reliquary (The Lost Caverns of Ixalan #10)
Eaten Alive (Innistrad: Midnight Hunt #99)
Eviscerator's Insight (Modern Horizons 3 #93)
Fanatical Offering (The Lost Caverns of Ixalan #105)
Kaervek's Spite (Visions #63)
Lash of the Balrog (The Lord of the Rings: Tales of Middle-earth #92)
Lethal Throwdown (Modern Horizons 3 #99)
Merciless Resolve (Shadows over Innistrad #123)
Mind Extraction (Apocalypse #42)
Morbid Curiosity (Battlebond #149)
Mutual Destruction (Ikoria: Lair of Behemoths #96)
Nasty End (The Lord of the Rings: Tales of Middle-earth #99)
Phyrexian Tribute (Mirage #134)
Powerstone Fracture (The Brothers' War #112)
Reckoner's Bargain (Kamigawa: Neon Dynasty #120)
Rite of Consumption (Shadowmoor #76)
Rite of Oblivion (Innistrad: Midnight Hunt #237)
Scapegoat (Stronghold #14)
Severed Strands (Double Masters 2022 #88)
Skulltap (Scourge #73)
Spark Harvest (Commander Legends #150)
Tendrils of Despair (Weatherlight #83)
Tormented Thoughts (Magic Origins #122)
Treacherous Greed (Murders at Karlov Manor #237)
Village Rites (The Lost Caverns of Ixalan Commander #212)
Wicked Reward (Visions #75)
Worthy Cause (Tempest #53)

The message was clear to Sorin—time to search for something else.