Augur of Autumn gives green decks access to the top of the library without immediately spending cards from hand. You can look at the top card at any time and play lands from there, while coven adds permission to cast creature spells from the top when you control three or more creatures with different powers. That can keep a creature-heavy deck developing through several useful top cards in a turn.
Additional land-play effects such as Exploration or Azusa, Lost but Seeking help clear more lands from the top. Fetch lands can shuffle away a card you cannot currently use, giving the Augur another chance to reveal a playable land or creature. The information also helps plan whether to cast a draw spell or preserve the current top card for another effect.
Coven checks creature power rather than mana value, creature type, or the number of counters present. A board of three creatures with identical power does not qualify. Counter placement and anthem effects can change whether the condition is met, so evaluate the actual powers after continuous effects are applied.
The Augur does not grant extra land plays or ignore normal casting timing. You still need mana for creatures cast from the library, and instant or sorcery cards can stop the sequence until you draw or move them. It fits decks with a high creature count, varied creature sizes, and enough ways to manage the top card that the extra access becomes a regular source of advantage.
