At the beginning of each of your postcombat main phases, return target Plant, Treefolk, or land card from your graveyard to your hand.
Build a Plant/Treefolk tribal go-wide or beatdown deck where Kirri's +2/+0 anthem turns small bodies into real threats, while the postcombat recursion engine grinds out repeatable value by returning Plants, Treefolk, and lands from your graveyard every turn. You ramp hard with Druids and land-fetch, flood the board with creatures and tokens, then attack into overwhelming pumped boards or fling lands/saprolings into a combo finish.
Built-in card advantage engine that recurs creatures and lands every postcombat main phase, making you very resilient to attrition
Anthem effect that meaningfully boosts an entire tribal board for free
Nald-green color access to the best ramp, land recursion, and token producers in the format
Tribal synergy spans both tokens (saprolings) and big midrange bodies (Treefolk)
Anthem only buffs power (+2/+0), doing nothing for toughness, so the board folds to sweepers and ground stalls
Recursion is slow and grindy—does nothing the turn Kirri lands and is easy to outpace by faster combo decks
Heavily reliant on Kirri being on the battlefield; she draws removal and the deck loses tempo when she's gone
Plant/Treefolk tribe is shallow, forcing some filler creatures that aren't great on their own