Since Sagas auto sacrifice once they hit the final chapter, generally only sticking around for three or four turns, you need some sort of engine to keep the Sagas on the battlefield
Shadowfax, Lord of Horses For just 5 mana, Shadowfax, Lord of Horses can come out, attack immediately, and cheat out another creature from your hand for free
Self-discard commander deck pairs
Dumping three or four lands while your hand is full of them can catapult you ahead of your opponents in terms of resources very early on, giving you a distinct advantage in the early game and potentially making you a huge target at the start of the game
Combining it with ETB creatures like or removal-proof threats helps you grind through long games
Legacy is for the players who want a stopgap between the most powerful cards of Vintage and the most recent cards