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It slithers toward people. Then, without warning, it triggers the explosion of its own head. It’s apparently one kind of Ultra Beast.
– Pokémon Ultra Sun Pokédex
Blacephalon is one of the new Ultra Beasts added for Ultra Sun/Moon. It looks weird, without any distinguishable facial features. It’s based on fireworks, or a clown, or something.
It has a signature move called “Mind Blown”, which is a 150 base special Fire move, but causes the user to lose half is HP.
Stat-wise, it has very high Attack and Sp Attack, and pretty good Speed, but its defenses are low.