The words 'oscillating slightly' are the very best part of this spell!

mix this with the new graviturgy subclass with the increased gravity ability for more damage

What would happen if a creature used their Legendary Resistance to make the Dexterity Save? They are still in a field of ongoing reverse gravity.

In this scenario there are no fixed objects for them to grab onto. Weird question I know but my character has this spell and the likelyhood of encountering Legendary creatures right now are very high.

I assume they might just dig whatever appendages they have into the ground hard enough to not fall? Or maybe through some sheer magical power the effects are a slower to effect them?

Quote from ElfBoyPorter >>

What would happen if a creature used their Legendary Resistance to make the Dexterity Save? They are still in a field of ongoing reverse gravity.

In this scenario there are no fixed objects for them to grab onto. Weird question I know but my character has this spell and the likelyhood of encountering Legendary creatures right now are very high.

 Based on the way the spell is written, I don't think the save is an option at all if there's no fixed object to grab onto, so there's no opportunity to use the legendary save.  Unless the ground is soft such that one could try to get a hold of something buried or the ground itself, or if there's some other reason to believe the save should apply despite lack of fixed objects.  But in general, this should be easy to DM because you can control the environment to some extent.

Though the awesome power of DM BS, his toes break through his boots and grip the floor tiles.

Combine with prismatic wall for uncanny damage

Quote from Kyreeeeeeeeee >>

Combine with prismatic wall for uncanny damage

Oh man... Oh man! 

I have already been percolating an idea for a "walking the Pattern\Logrus" sort of ordeal, & trying to think of ways to effect the walls\veils presented, as canonically as possible... Having a Prismatic Wall spring up as soon as you begin, is definitely one way to up the stakes!

Is Disintegrate the only other spell that calls for a lodestone? 

What would the ruling be if I wanted to change my material components to the fingerbone of a vampire?

So notably it says that creatures in the area when you cast it are flung to the top of the reversed gravity, logically speaking so would any unprepared new creature that tries to wander in though wouldn't it, unless you dropped the zone anyone entering the area should technically fly upwards, or does the magic not affect the whole area for the whole duration?

Regardless the area this can be used on is huge and unless you've got wings is for sure one of the best ways to stop anyone from entering said large area.

What would happen if two mages cast this on the same area?

One possible ruling: They would somewhat cancel each other out, and creatures and unsecured objects would end up floating in the middle as long as both concentrate. if one drops and the other maintains, everything would fly to the top. if both drop at once, things would fall the half height (50ft) down. This is all assuming there are no obstacles in the way, like if it's cast outdoors.

What would happen if 2 mages cast this in a 30ft ceiling room? 

RAW, nothing, but feel free to homebrew

Insert whatever noise C-moon will make

Do you believe in 'gravity'?

Quote from ElfBoyPorter >>

What would happen if a creature used their Legendary Resistance to make the Dexterity Save? They are still in a field of ongoing reverse gravity.

In this scenario there are no fixed objects for them to grab onto. Weird question I know but my character has this spell and the likelyhood of encountering Legendary creatures right now are very high.

 If there isn't anything to grab a hold of, the creature doesn't make a save. It's affected by the spell regardless. If there is something to grab a hold of, it can use a legendary resistance to succeed on grabbing hold of something.

The Great Oscillating One!

Question:  If this is cast in a place with a ceiling (let's use a 30' ceiling as an example)...  Does someone affected by this spell take falling damage when they hit the ceiling?  And then would they take the same hit dice of damage when the spell is dropped if they fall?

yes, thats what the spell says

So.... If my party was on a boat that was being attacked by sea creatures, could I use this spell and center it below the water?  I'm thinking that any water breathing creature that was in the area would be lifted out of the water and held there as long as I hold concentration.  Yes? No?