The new Ranger ability, Favored Foe, says:
When you hit a creature with an attack roll, you can call on your
mystical bond with nature to mark the target as your favored enemy for
1 minute or until you lose your concentration (as if you were
concentrating on a spell).The first time on each of your turns that you hit the favored enemy
and deal damage to it, including when you mark it, you can increase
that damage by 1d4.You can use this feature to mark a favored enemy a number of times
equal to your proficiency bonus, and you regain all expended uses when
you finish a long rest.
Since the ability says that you mark the creature when you hit it and that you can use this feature a number of times equal to your proficiency modifier. I am wondering if you could target two creatures in the same turn, since you have Extra Attack at 5th level, to maximize the damage you can deal in a turn.
The scenario I imagine is the following, you attack creature A and mark it, then with your extra attack you attack creature B and mark it. On your next turn, you again attack creature A & B so you can use the "The first time on each of your turns that you hit the favoured enemy" clause of Favoured Foe ability to deal the extra damage since both creatures got hit only once on its turn.
Would this work?
Best Answer
No, as marking a foe requires concentration.
Favored Foe states (emphasis mine):
"As if concentrating on a spell" indicates that the usual rules for concentration on spell effects applies here.
The rules for breaking concentration say:
Marking a second foe would end your concentration on the first mark, since it requires you to concentrate on the second mark.