Magnus

Whelp, time to find out how much +ATK each star gives past 7.

But my god...+1,124,424 range just from those 3 equips alone...

11, 12, 13, 14, 15, 16, etc.
It's a simple pattern. All Stats will increase by the last increase plus the number of stars. For example, if the first star gives x stats, the second will give (x+1), the third will be ((x+1)+2), etc. Attack is easier, it's just +1 every time. x, x+1, x+1+1, etc.

I dunno if every star from 6 and beyond will give attack, though, seems that way.