FlyingFlying is an evasion ability.
A creature with flying can’t be blocked except by creatures with flying and/or reach. A creature with flying can block a creature with or without flying. (See rule 509, “Declare Blockers Step,” and rule 702.17, “Reach.”)
Multiple instances of flying on the same creature are redundant. (CR 702.9)
Whenever The Wise Mothman enters or attacks, each player gets a
rad counterRad counters are a kind of counter a player can have (see rule 122, “Counters”). There is an inherent triggered ability associated with rad counters. This ability has no source and is controlled by the active player. This is an exception to rule 113.8. The full text of this ability is “At the beginning of each player’s precombat main phase, if that player has one or more rad counters, that player mills a number of cards equal to the number of rad counters they have. For each nonland card milled this way, that player loses 1 life and removes one rad counter from themselves.” (CR 728.1).
Whenever one or more nonland cards are milled, 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 each of up to X target creatures, where X is the number of nonland cards milled this way.