A new mirror will always be black and has no knowledge of any destination. You can not teleport by using it yet.
Rightclick with it while pointing to something to set the mirror's destination. The mirror will magically remember your position and it becomes gray.
To teleport to the previously set position, leftclick with the mirror once. This will make a loud sound at both source and destination and creates a lot of visible particles, so you will probably catch the attention of others.
You can set a new mirror's destination with a rightclick, but the mirror will then forget the previous destination. A mirror does not have that much memory, after all.
Screenshot shortly taken after teleporting:
If you have the Mana mod installed, using the mirror comes at a mana price:
- Setting the destination: 20
- Teleporting: 200
The itemstring of a new mirror of returning is “returnmirror:returnmirror”. Use /giveme or creative mode to obtain it.
License of everything: WTFPL
Works in Minetest 0.4.16 or later
Git project page (with readme file): http://repo.or.cz/minetest_returnmirror.git
Mandatory dependencies: None.