Vestiges Are The Passsive Skills You Can Get While In A "Run".
- Bottom Right Side Of The Screen, There's A Bunch Of Empty Circles, These Are The Slots You Need To Fill.
Once You Fill All Those Slots, The Achievement Pops.
Good Luck!
*Side Note*
Getting An Additional One Will Give You The Option To Replace One Of Your Current Vestiges, Dropping The Old One On The Ground.