Beseech the Mirror

In Commander, Beseech the Mirror is firmly in the top tier of black tutors — the Bargain mode converts a Treasure or other sacrificeable permanent into a free cast on whatever you find, which collapses the traditional two-step of tutor-then-cast into a single action. Competitive Commander decks that generate cheap sacrifice fodder treat it as an upgrade over Demonic Tutor in the right context, since the floor (a four-mana Vampiric Tutor to hand) is still acceptable and the ceiling (free combo piece onto the battlefield) is broken. In Legacy and Vintage, it competes against Vampiric Tutor and Demonic Tutor directly, and the Bargain restriction to mana value four or less limits its appeal in formats where you want to cheat an Emrakul into play. Modern and Pioneer see it in black combo strategies that produce Treasures — Beseech the Mirror earns its slot there when the deck can consistently hit the Bargain condition. Standard legality made it a format-defining card in its release window for the same reason: sacrifice-synergy shells could tutor and cast on the same turn at a mana cost that felt fundamentally unfair at the kitchen table level.