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
Avacyn Restored (AVR)
• #200Rulings
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)