Worldsoul's Rage
Most X burn spells buy their flexibility with a downside baked into the fine print: they scale into the late game and then leave you tapped out, having done nothing but point damage. This one pays you back for the same cast. Every point of X doubles as a land you get to drop tapped from hand or graveyard, so sinking ten into it burns for ten while rebuilding a mana base to keep going. The graveyard clause is the part doing the real design work; pulling lands you have already fetched or milled turns spent duplicates into stored mana you get to cash a second time. That rewards a deck built to stock a yard with lands and unload the pile in a single turn, and it resolves the oldest problem with the big finale spell: the topdeck that ends a threat but leaves you with nothing behind it. Here the follow-up funds itself. Damage and development riding on one Gruul sorcery is a rare pairing, and the recursion clause is what fuses the two halves into a single effect rather than a graft. It is a payoff card that also refills the tank that paid for it, which is why a late-game draw off the top reads as reach and ramp at once rather than one or the other.
