The Tarrasque has haste and ward as long as it was cast.
Whenever The Tarrasque attacks, it fights target creature defending player controls.
Cast a 10/10 haste, ward 10 beater that's nearly impossible to remove once it hits the battlefield, then beat down while its fight trigger clears blockers and applies pressure. You ramp hard in the early turns, deploy The Tarrasque around turn 5-6, and either go wide with stompy creatures or load up Voltron equipment to close games fast.
Ward 10 makes it extremely resilient once cast — almost no spot removal can touch it
Haste means immediate impact the turn it lands
The fight trigger doubles as removal, clearing blockers each attack
Mono-green has the best ramp in the format to deploy it ahead of curve
Big body that pressures all three opponents quickly
Ward only applies if it was cast — recast from command zone gets pricey fast, and tokens/copies lose ward
9 mana is steep without dedicated ramp
No evasion or trample on its own, so chump blockers can stall it
Vulnerable to board wipes, sacrifice effects, and edicts that bypass ward
Mono-green struggles with non-creature permanents and card advantage at the top end
Protects your board from the wraths that are The Tarrasque's main weakness.
Add trample enablers like Rancor, Loxodon Warhammer, or Garruk's Uprising so the fight trigger and combat actually convert to damage. Lean into fast ramp (Nature's Lore, Cultivate, Carpet of Flowers) to deploy it by turn 4-5, and pack protection like Heroic Intervention and Bristly Bill against the board wipes that are its only real answer. For higher power, include deathtouch granters such as Nylea or Snake umbra to make every fight a guaranteed kill.
Legendary Creature — Dinosaur
as long as it was cast.