It allows you to grow your creatures to unlock board stalls, while enabling some very interesting synergies by dishing out creature abilities to your team
They do not attack with Elvish Reclaimer, which, with 3 cards in hand, leaves freak scenarios like double Elvish Spirit Guide + Stifle as potential avenues to win, but unlikely
Its a heavily-played card in formats where its legal, and thats mostly Vintage, Legacy, Cube, and EDH, where its a Game Changer
For example, if you discard Carnage, Crimson Chaos, you may cast it from your graveyard for the remainder of the turn by paying just rather than the normal cost
You pay all costs and follow all timing rules for cards played this way
For added survivability, Rocky Helmet provides extra defense, and Leaf offers a quick retreat option if the battle gets too intense