Ramp strategies have existed forever. You have them in Standard, versions in Modern—but they aren’t anything quite like what is available in Legacy.
Cloudpost is bananas. B-a-n-a-n-a-s. Each additional Locus will cause each Cloudpost to tap for an additional mana. That means 2 Cloudposts tap for 4, and 3 will tap for 9. There is only one other Locus, Glimmerpost, which conveniently will gain you a bunch of life while setting up. You also have Vesuva and Thespian’s Stage to give you more Locuses and more mana.
Candelabra of Tawnos goes back to the very early years of the game, but can create some explosive mana. Have those 3 Cloudposts I mentioned earlier? Candelabra means that you have access to 17 mana. That’s some serious scaling.
You also have access to truly awesome tutors for lands. Crop Rotation is a 1-mana way to turn any land into exactly what you’re looking for, while Expedition Map crosses over from Modern Tron as a viable way to keep the ramp coming.
From there, you need a payoff, and the options in Legacy are limitless. Primeval Titan makes the cut in most versions as a spell that can be cast far earlier than it should be, can ramp you, and can also help tutor for things like life gain (Glimmerpost) or shut down entire attacks (Glacial Chasm). With other utility lands to get with Titan, Crop Rotation, and Map such as Bojuka Bog and Cavern of Souls, you have extra tools to fight a variety of matchups.
The other clear payoff: all of the Eldrazi! Emrakul, the Aeons Torn, Kozilek, the Great Distortion, and Ulamog, the Ceaseless Hunger are all feasible to cast—potentially as early as turn 3. Platinum Angel and Platinum Emperion are other potential payoffs that come at a cheaper cost, and many decks in the format can’t beat them.
With all of these Eldrazi and huge threats, many versions go the blue route for the best way to cheat giant things into play. Show and Telling an unbeatable indestructible monster into play is a great feeling. You also get access to Brainstorm to help find the critical tools and shuffle away the excess stuff you don’t need or can’t use.
The 12 Post deck is another one of the coolest decks in Legacy and fights on a different axis. It lets you cheat something awesome into play or cast it extremely early. You also happen to boast one of the best matchups in the format against what many feel is the best—and most annoying deck—in Miracles!
If you enjoy ramp strategies or doing the biggest, coolest things, then 12 Post is probably the deck for you!