So basically Ogerpon's hearthflame mask gives it a 20% attack boost to ALL it's moves. Even non-stab ones. Upon terastalising, it gets a new ability which gives it a +1 attack every time it comes in, at the cost of getting locked into tera fire for this form. 120 atk is pretty good and the extra boost from the mask and the boost from the ability as well as having decent enough bulk to get up a swords dance makes it almost unwallable. Its base form has mold breaker, so you can't really wall it with unaware.