Unknown Monster

Where can i exactly find Number 156??I need it for Angelon.

It’s northwest of Windon, in the spot on the brown mountains. (Cherub)

Is it rare?

Fairly, yes.

its hard to catch though, it killed itself with me using a heal move, and its catch % was low, 38% and i have 3 lvl 99’s and im on the last first one

Maybe bring stun arkadions? That seemed to be suggested a lot and it sounds effective.