Its an endure X ability, where the X is determined by the number of counters on Warden of the Grove
Aside from the three cards that have been revealed so far, its likely that this second set in the Mega Evolution era will also feature new Mega Evolution cards that werent available in the first set
Head-to-Head Comparison: Booster Bundles vs
Whatever works
Creatures (32) 2 Kenrith, the Returned King 3 Rimrock Knight 1 Taranika, Akroan Veteran 4 Winota, Joiner of Forces 4 Selfless Savior 4 Staunch Shieldmate 4 Luminarch Aspirant 4 Magda, Brazen Outlaw 4 Clarion Spirit 2 Usher of the Fallen Lands (24) Spells (4) Continuing my obsession with Dwarves, Treasure, and six mana on Turn 3, Clarion Spirit makes non-Human tokens
For example, Iriss Fighting Spirit , allows you to discard a card from your hand for the opportunity to draw until you have six cards