Energy Refractor

The two-mana replacement-cantrip mana rock is a shape that keeps recurring because it solves a narrow problem: fixing that does not cost you a card. Pay two, get a card back on entry, and the artifact then sits on the board as an any-color source that only ever taxes you two more mana per activation. That last clause is the honest price. Most fixing rocks add mana for free once they resolve; this one charges every time, so it is never the accelerant a Signet or a Talisman is. What it buys instead is smoothness without card disadvantage: the draw trigger means the slot is close to free in a deck that needs colors more than it needs speed. This is the old fixing-versus-tempo problem split down the middle. A land drop fixes without a card cost but does nothing else; a Signet ramps but costs a card; this refunds the card and surrenders the ramp. That makes it a filler-grade utility artifact rather than a build-around, which is exactly what it was drawn to be: a low-friction way to keep a color-hungry deck's hands functional, with the pay-two activation acting as the ceiling that stops it from ever becoming a genuine mana engine.