Transgress the Mind

In Commander, Transgress the Mind punches above its weight because the three-cost floor hits the vast majority of threats that matter — combo pieces, counterspells, board wipes — and the investigate trigger cushions the card disadvantage you'd normally eat from a discard spell. In Modern and Pioneer it competes against cheaper options like Thoughtseize and Inquisition of Kozilek, which don't come with a clue but cost one mana less and hit smaller targets; Transgress the Mind rarely makes the cut there outside of very specific Eldrazi-tribal shells. Legacy and Vintage have even stiffer competition and faster clocks, so it's a fringe inclusion at best. Oathbreaker follows Commander logic — two mana is acceptable, the exile matters, and it's a clean answer to a signature spell or key hand piece.