Where to find Blacephalon in Sun, Moon, Ultra Sun & Ultra Moon

Only in Ultra Sun
Static Encounter: Poni Grove
Walk: Poni Grove (100%)

Blacephalon also appears in

How to get Blacephalon in Sun, Moon, Ultra Sun & Ultra Moon

For the look, the best colour match is Heal Ball or Beast Ball.

Blacephalon in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)