Emergent Growth

The +5/+5 is the bait; the "must be blocked this turn if able" clause is the actual spell. It forces the defender to commit at least one blocker to your creature, which turns a pump into a soft removal proxy: point it at something with deathtouch and the compelled block becomes a trade the opponent never wanted to make. This is the older lure trick stapled to a five-point swing, collapsing two effects into one card and one decision. The sorcery-speed limit does the restraining work: it only fires on your turn, before blockers assign, so the opponent watches the +5/+5 resolve and then picks the least-bad legal block rather than getting ambushed mid-combat. That telegraphing is why a four-mana spell isn't a clean two-for-one every time. Its ceiling depends on the gap between "must be blocked" and "blocked profitably," and note the load-bearing "if able": the clause only compels a block the defender is actually capable of making. An unreachable flier forces nothing, because no creature can legally block it. The spell rewards a board where the opponent has ground blockers who lose the exchange (a deathtoucher that trades up, an attacker big enough to punch through the chump they're forced to throw). Cast at a defenseless opponent, it reverts to an oversized combat trick. The attacker sets the terms, but only when the defender has bodies that can answer the summons.