Infinite Mana Piece

Cards that serve as the keystone half of well-known infinite mana loops, either by producing more mana than they cost to untap, by untapping a board of mana sources cheaply, or by copying or replaying activated abilities to multiply output. Basalt Monolith pairs with Power Artifact or Rings of Brighthearth; Dramatic Reversal goes infinite with any nonland mana rocks totalling three or more; Isochron Scepter imprints Dramatic Reversal for the same loop. Narrower than mana_combo.mana_untapper, which covers untap effects generally including ones that don't loop; distinct from mana_combo.mana_doubler, which scales each mana ability rather than enabling a closed loop, and from mana_combo.mana_sink, which spends the resulting infinite pool.