Moon Rocks are hard to come by so a Meteor Staff would make it a lot easier.
For PVP protection:
In PVP, works everywhere.
In PVE, works only in Meteor affected biomes
Meteor Staff:
1 Yellow Moonlens (representing the Sun and the Moon, i guess?), 2 Logs, 3 Marble (not sure on Marble, it seemed too simple even with a Yellow Moonlens)
Research Tier: Magic One/Prestihatitator
10 Uses
For every use, it will cause a Meteor Shower to start (if in a valid area) and take 10% off the durability. In addition, you lose 30 Sanity.
If used in a non-valid biome, your character will comment "It doesn't seem to work here." or something to that effect.
This helps people to farm Moonrocks, without being available too easily.
Naturally it would show up on the Map when dropped, like an actual Moonlens. Unsure if this would change in the valid biomes or not.