Double Major

Copying a creature spell on the stack is the cheapest kind of value doubling the game offers, because the copy resolves as a token that keeps every enters-the-battlefield trigger the original carries: double the etb, double the counters, double the body, all for two mana. The payoff scales with whatever you were already casting, so the fork demands only that your deck run a creature worth cloning. The legendary carve-out is the honest tax. Ordinarily the copy token and the original legend would eventually share a name on the battlefield, and one would die to the legend rule; here the copy comes in non-legendary, sidestepping the wasted mana and turning your marquee legend into a genuine two-for-one rather than a fizzle. That single clause is what makes the fork worth casting on precisely the cards you most want to fork, where earlier blue-green copy effects either barred legends outright or left you eating the legend rule. The timing is subtler than it looks, though. This resolves first and puts a copy of the creature spell on the stack, then all players receive priority; that copy later resolves into the token, and an opponent has a window to answer it (bounce, removal, a counter on the trigger) before your original ever lands. It rewards a deck leaning on one high-impact creature spell rather than a wide board of small ones, a narrower ask than the mana cost suggests but a sharper one.