I think we have a pretty good handle on this ruling but wanted to get a couple of outside opinions.

The scenario is this. The domain counter for gravity rift was revealed on a wormhole space tile. Does the gravity rift replace/negate the wormhole or do the two coexists?

Thanks

Gravity rift is also present with a planet (Cormund tile) so I think it can coexist with the wormhole. Moreover the token description does not say to erase whatever was in the tile. Anyway I don't remember if there is any FAQ about this (maybe you'd better to check them).