Portal Mirrors are used a lot by oracles in order to see the future. For all oracles, it is the mind that can see into the past, future, present. By using the Portal Mirrors, they can see more vividly what they saw, and can even pause, rewind, and fast forward the vision. This can also be used for a teleportation device. With a Portal Mirror, the user could travel anywhere in existence depending on the users mana.
The Oracle used her Portal Mirror to travel into her secret garden, only accessible by teleportation.