When there is fire in me then I am still cold. When I own your true love's face then you will not see me. To all things I give no more than I am given. In time I may have all things, and yet I can keep nothing. What am I?

Why this works

This riddle plays with the multifaceted nature of a mirror and its reflections. The phrase "fire in me" refers to the reflective surface of the mirror, which can shine or sparkle like flames but is physically cold to the touch. The line "when I own your true love's face, then you will not see me" suggests that when you look into a mirror, your focus is on the reflection (your love's face) rather than the mirror itself, making it seem invisible. The final lines highlight that a mirror reflects whatever is placed before it, giving back only what it receives, and though it can reflect all things, it cannot hold onto any of them. This clever interplay of imagery and meanings makes the answer "a mirror" fitting and thought-provoking!