Xenoblade Chronicles 2: that waifu that you do

I have no idea how long this game is, but I’m already in it like 70 hours or so, and I kind of feel like I’m not even half done.

Also, finally unlocked Poppi’s second form, which gives a lot more flexibility in terms of combos.

Can anyone explain exactly what causes an elemental orb to show up? I think it has something to do with landing a 3rd tier blade combo? But it doesn’t always seem to?