Skulduggery

In Commander, Skulduggery is fringe at best — the effect only matters in combat math, and you need exactly the right board state for it to generate real value. Pauper is where Skulduggery has the most plausible home, since commons-only environments reward cheap tricks and combat manipulation more heavily, and a single mana to trade a durable blocker for a fragile one can swing a race. In competitive formats like Modern and Legacy, it simply doesn't clear the bar — there are cheaper, unconditional removal spells that don't require an opponent to have a creature with the right stat spread. Pioneer and Standard give it the most charitable read among 60-card formats, mostly in aggressive black shells that want to force through damage, but even there it rarely makes the cut.