Feeling obligated to return a favor, share resources, trade an item, etc.
"in a way? you can have a multiplayer world with others, but you can't join anyone else's world without communicating between yourselves first"
"You can donate or receive materials everyday, from your guild members or friends outside of your guild. The game encourages this donate x donate system."
"Allows you to create and share maps with other players. Basically a mod system. Please inform me if this does not fit the criteria."