| Piccolo |
I don't know where you got the "agile" part of the name, but any mithral armor counts as one category lighter.
Interestingly enough, you can take the Armor Expert trait and combine it with a mithral breastplate, and you can not only sleep in the armor, but you can also wear it without proficiency or penalty aside from having a max of +5 dexterity bonus to AC.
A Rogue could wear one and not have trouble, same goes for a mithral Heavy shield (no armor check penalty, so no lack of proficiency penalty).