Both Time Materia and Cait Sith's Limits are incorrect. Although TIME is written down the side on purpose.

Hint: The "it" in line 3 doesn't necessarily equal the "it" in line 2 (which does equal the "one" in line 1), which implies that there could be more than one entity involved in the answer to this riddle.

This isn't an elegant riddle, by any means. :shame: