Granted, she wears the costume well...but good looks don't count for much against Boneyard and the other ultra-villains Mantra seems to run across so regularly. Fortunately, Archimage also saw fit to provide her with the powers she'd need to survive in her dangerous new occupation.
White magic, black magic, and a note on the heredity of wizards
Power has its price...
Attractive and functional. She doesn't wear it just for the good looks, you know...
Aside from her regular costume, Mantra has also tracked down a number of mystical artifacts. (Now where did I put down that grail...?)