I ran away from Zygarde..?

Question

So I found Zygarde, but all I had were Pokeballs and Luxury balls, so I ran away to get Ultra and Dusk balls. After I ran away, my game said he faded into the shadows... Do I have to defeat the Elite Four like if I had knocked him out? Or will he be back next time I go into Terminus Cave? Please help!

Answer 1

He will return after every time you beat the E4. I fainted it and I returned after I beat the E4 again.

Source: Exp points(experience)

Comments

The real question for me is, if fainting it or running away will reset its stats, or will it come back the same exact Zygarde as before. :)

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Same for Mewtwo

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ALL legendary pokemon that, when fainted or you run away, say : "'Name' went off somewhere..." or the like, you beat the E4 and Champion to re-enable them.

Answer 2

He will return after you beat the Elite Four as if you knocked it out.

Source: Experience