Last March of the Ents turns a creature with high toughness into a large refill and a new battlefield. It draws cards equal to the greatest toughness among creatures you control, then lets you put any number of creature cards from your hand onto the battlefield. The creatures drawn by the first part can be included in the second, creating a powerful connection between the size of your existing board and the next wave of threats.
Green creature decks can use a durable body to establish the draw count before casting the spell. Creatures with valuable entry abilities, such as Eternal Witness or Avenger of Zendikar, reward being put directly onto the battlefield. Expensive creatures become easier to deploy in quantity because the effect does not ask you to pay their mana costs individually.
The spell cannot be countered, but opponents can still respond by removing your highest-toughness creature. The draw amount is determined as the spell resolves, so keeping another substantial creature available reduces that vulnerability. You can still put creature cards already in your hand onto the battlefield even if the draw portion ends up smaller than expected.
Putting creatures into play is not casting them. Cast triggers such as Kozilek, Butcher of Truth's draw ability do not happen, while entry triggers do. Build the payoff package around that distinction, and cast Last March when your existing creature, remaining hand, and likely draws combine to justify its eight-mana investment.
