Ulvenwald Tracker
Creature — Human Shaman
, 
: Target creature you control fights another target creature.
"Peace will come to Innistrad, but only after all abominations have been dealt with, one by one."
Christopher Moeller
Modern Masters 2017 (MM3)
• #144Rulings
The second target of Ulvenwald Tracker’s ability can be another creature you control, but it can’t be the same creature as the first target.
(wotc • 2017-03-14)
If either target of Ulvenwald Tracker’s ability is an illegal target when the ability tries to resolve, neither creature will deal or be dealt damage.
(wotc • 2017-03-14)
Rulings
The second target of Ulvenwald Tracker’s ability can be another creature you control, but it can’t be the same creature as the first target.
(wotc • 2017-03-14)
If either target of Ulvenwald Tracker’s ability is an illegal target when the ability tries to resolve, neither creature will deal or be dealt damage.
(wotc • 2017-03-14)