Here's what the data shows for Mono Green Landfall in Standard across 81 tournament entries (2025 onward):
Mossborn Hydra is essentially a staple of the archetype. It appears in 79 of 81 registered decks (97.5% presence) at nearly 4 copies on average, making it a near-universal 4-of. The two decks that ran it without Mossborn Hydra in the main went 3-7 (30.0% winrate), while the 79 lists that did include it went 139-201 (40.9% winrate), a meaningful 11-percentage-point gap. That said, sample size for the "without" group is tiny (only 10 matches), so treat that gap as directional rather than definitive.
The broader picture for the archetype is rough regardless. The overall non-mirror winrate sits at about 40.6%, which is below the 50% threshold you'd want from a competitive archetype. The core shell is consistent: Sazh's Chocobo, Snakeskin Veil, Tifa Lockhart, Fabled Passage, and Traveling Chocobo all show up in 95%+ of lists alongside Mossborn Hydra. The data strongly suggests running Mossborn Hydra as a 4-of main deck is the consensus correct build, but the archetype as a whole is underperforming in the current Standard meta.
Sources: Data drawn from 46 Standard tournaments (72% MTGO, 28% Melee). Sample tournaments include: