EvolveEvolve is a triggered ability. “Evolve” means “Whenever a creature you control enters, if that creature’s power is greater than this creature’s power and/or that creature’s toughness is greater than this creature’s toughness, put a +1/+1 counter on this creature.”
A creature “evolves” when one or more +1/+1 counters are put on it as a result of its evolve ability resolving.
A creature can’t have a greater power or toughness than a noncreature permanent.
If a creature has multiple instances of evolve, each triggers separately. (CR 702.100) (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1
counterTo counter a spell or ability is to cancel it: remove it from the stack without resolving it. A counter on an object or player is instead a marker that changes characteristics or interacts with rules or abilities; for example, a +1/+1 counter modifies a creature’s power and toughness. (CR 701.6; 122.1) on this creature.)
When this creature
diesIs put into a graveyard from the battlefield. (CR 700.4), you may
discover“Discover N” means “Exile cards from the top of your library until you exile a nonland card with mana value N or less. You may cast that card without paying its mana cost if the resulting spell’s mana value is less than or equal to N. If you don’t cast it, put that card into your hand. Put the remaining exiled cards on the bottom of your library in a random order.”
A player has “discovered” after the process described in 701.57a is complete, even if some or all of those actions were impossible.
If the final card exiled during the process described in rule 701.57a has mana value N or less, it is the “discovered card,” regardless of whether it was cast or put into a player’s hand. (CR 701.57) X, where X is its toughness.