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)
MentorMentor is a triggered ability. “Mentor” means “Whenever this creature attacks, put a +1/+1 counter on target attacking creature with power less than this creature’s power.”
If a creature has multiple instances of mentor, each triggers separately.
An ability that triggers whenever a creature mentors another creature triggers whenever a mentor ability whose source is the first creature and whose target is the second creature resolves. (CR 702.134) (Whenever this creature attacks, 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 target attacking creature with lesser power.)
When this creature
diesIs put into a graveyard from the battlefield. (CR 700.4), 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 white creature you control.