I can see it being both things. A powerful gem which power may be used to save this world or balance it, or to destroy and ruin it if said power is used for something else. Like getting a bunch of foreigners to their worlds.

The bad part would be that we would be the responsible of destroying this world, the good part would be that we wouldn't be here to know it. And if we were to decide to not use the wish to get us home, we would save this world, but we would end locking in this world forever.

[Ikki just loves to go for the worst possibilities.]