Rupee is the ultimate source of power in the MCRPG universe. You use it to:

WARNING Rupee is a very ephemeral resource - when you die, some of your reserves slip away. Players lose 10% of their rupees upon death!

VIPs only lose 5% of their rupees upon death!

How can I get rupees?

Rupees are represented on the map by Emerald Ore. Simply mine it, and your rupee reserve will increase by 1. Pickaxes with the Fortune enchantment increase the amount of rupee you get from mining.

There are 3 ways for you to get rupees.

The rupee mine

At 0,0 there is a large deposit of rupee. Go there and mine to your heart's content. But be wary of other players nearby!
Rupee Mine

Killing other players

When you kill another player, 25% of their rupee reserve is distributed between all players within a 16 block radius of where they died.

Raiding bases

Finding and breaking into a well defended Structure is probably the most difficult, but most rewarding way to earn rupees. You must invest enough rupees to become the owner of the structure. Then you can demolish the structure to extract out all the rupees that has been invested in the structure. However(!), if the owner of the structure has invested more rupees in it than you can afford, you won't be able to get your rupees back out!