My guess is Time Magic

Halfway along its journey it was in a class of its own - In FFV, Time Magic had its own class.
Now it's been bleached and dispersed - Some were put in White Magic (Haste, Slow, Regen, Reflect), and some in Black Magic (Demi). Also, 'bleached' could be Demi only doing 1/4 HP damage in FFX, not 1/2.
Except for one that's darkened over the ages - Not sure
A few can be seen, but never had - Some time magic is only used by opponents, like Quarter (now called Gravija) and Mute (Silence).
Many paths must be travelled to get the rest - You have to go all over the Sphere Grid to get the spells; Haste and Slow are in Tidus' grid, Regen and Reflect in Yuna's grid, Demi in Lulu's, etc.