Shitty res image aside, I'd be surprised if the third legendary wasn't Ouroboros.
Zygarde already covers that though.
>>26710052
O-ouroboros?
>>26710126
Zydog = Fafnir
Zyguard = Jourmagnd whatever
Perfect Zy = that other child of loki
>>26710134
An actual Ouroboros, not a Tsuchinoko.
>>26710263
oh fuck meant that for >>26710126