Like most Magic: The Gathering cards, the value of Sorin the Mirthless depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Magic Online Promos)
Really, though, its the unblockable ability which turns this from okay to wow, pretty neat
Dragons and Goblins, Red
Making pulling a showcase leader extremely valuable
Decklist: LED Dredge in Legacy Creature (22) Golgari Thug x3 Narcomoeba x4 Satoru, the Infiltrator Thassa's Oracle Poxwalkers x3 Stinkweed Imp x4 Anger Golgari Grave-Troll x4 Ox of Agonas Enchantment (3) Artifact (4) Instant (6) Otherworldly Gaze x4 Dread Return x2 Sorcery (11) Breakthrough x2 Cabal Therapy x4 Careful Study Faithless Looting x4 Land (14) Cephalid Coliseum x4 Island Mountain Scalding Tarn x4 Underground Sea Volcanic Island x3 Sideboard (15) Into the Flood Maw x4 Echoing Truth Shenanigans x2 Leyline of the Void x4 Unmask x4 While milling cards, youll come across free Narcomoebas that slowly chip in at your opponents life, or sometimes block to preserve your life total
The Multicolored Cards of Modern Horizons 2 The First Sliver is by far the most valuable multicolored card, at $85.13, since granting cascade to all Slivers can generate some incredible value