Let the Galaxy Burn

A one-sided board wipe with a scaling knob, which is a rarer thing than it sounds. The exemption for creatures that entered this turn is the clause that separates it from every symmetrical X-damage sweeper, and the reason it matters is entirely about sequencing on your own turn. Because this is an X spell, its mana value on the stack is X plus 6, so cascade digs for a nonland card costing less than that total: pump X, and the cascade reaches deeper. That coupling is the point, and it runs in a specific order. Cascade triggers when you cast this, so the free spell resolves first, while Let the Galaxy Burn is still waiting underneath it on the stack. If cascade flips a creature, that creature enters before the damage lands, which means the "didn't enter this turn" clause protects it: your free body walks away clean, and the sweep clears everyone else's board around it. The same number that widens the wrath also sizes the spell you get off the top and, potentially, the creature that survives to inherit the empty battlefield. What it asks in return is patience. It is a sorcery, so both the sweep and the cascade land on your turn, and you want your own creatures either held in hand for after or, better, arriving off the cascade itself rather than committed before the spell went on the stack. The ceiling is a board reset that leaves you the only one still standing.