Spellwoven Robes
These robes are spun from special, magic-sensitive threads, causing arcane glyphs to appear on the robe while you wear it whenever you cast a spell. While wearing these robes and no other armor, your AC is equal to 10 + your spellcasting ability modifier. In addition, whenever you cast a spell of 1st level or higher, you can change the apparent style, color, and apparent material of the robe. Regardless of its appearance, it is always a robe and its weight remains the same.
"Some bards choose to pattern their protective robes with glamorous imagery and flourishes of color. Clerics will oft depict symbols of their chosen deity or faith with colors to match. Me? Well, let's just say that I'm a woman of many tastes and shifting interests." -Overheard conversation between Omer the tavernkeep and the legendary sorceress Yahl-rutan.