OP: Your room is 85 feet tall ????
Okay, that's a case where Jeremy Crawford's mantra applies to all the rules as written answers.
Spells make Exactly What they say
Level 7 transmutation
This spell reverses gravity in a cylinder 50 meters in radius and 100 feet in height centered on a point within range. All creatures and objects that are not anchored to the ground in the area fall upward and reach the top of the area when you cast that spell. A creature can make a Dexterity save throw to grab a fixed object that it can reach, thus avoiding falling.
If a solid object (such as a ceiling) is encountered in this fall, objects and falling creatures will hit it as they would during a normal fall. If an object or creature reaches the top of the area without touching anything, it stays there, swinging slightly for the duration.
At the end of the duration, the affected objects and creatures fall back.
Gravity is reversed, things fall. Cool. You fall to the ceiling or are suspended on the ground. Right? Okay, we all agree here.
Cloud of Meteors
Evocation level 9
Flaming fire orbs collapse on the ground at four different points you can see in range. Every creature in a Sphere of radius of 40 feet centered on each point you choose must make a backup roll of Dexterity. The sphere extends around the corners. A creature takes 20d6 fire damage and 20d6 blunt damage in case of failure of a save, or half less damage if successful. A creature in the area of more than one fire explosion is affected only once.
The spell damages objects in the area and ignites flammable items that are not worn or worn.
Flaming globes appear and collapse towards the targets. He does not say:
- How serious he used
- Where the orbs appear
- What inertia they already have from wherever they have been drawn.
They appear and collapse towards the targets. If it means that they appear "below"
them and fall up or over them and fall or if they magically fall sideways – because magic – then they fall sideways. Whatever the direction in which they collapse, they collapse to the targets.
So, if you're hanging on the ground or falling off the ceiling, they may appear "above you" closer to the ground than you are currently doing and move in your direction, or they may already have a huge inertia to overcome the effects of the reverse gravity spell. I do not care what you do narratively to convince you and convince your players Why it happens – the spell says what it does.
From a fairness point of view, would you let someone climb to the ceiling and leave a level 9 spell to allow him to miss it because of the word "lead"? No, that's right, because it would be cheap. It's a level 9 slot machine.
I will not get lost in the definitions of the word "soil" in this context. When gravity is reversed, is the floor or ceiling "crushed"? I do not know and I do not know It just has to make sense with the story. If we keep a precise definition of the ground, the spell could never be launched in open water, under water, in planes like the astral plane or Pandemonium because "the ground" does not work as we think here on our land at these places. . And this is not what is planned.
Dots, not creatures
The "one point you choose" does not have to be on the ground. This can be in the intestines, the head or something else. In addition, the area of effect for each of the 4 points is the origin of a 40 feet Ray sphere which has a diameter of 80 feet. So if the piece in question is not 85 feet high, the whole debate is irrelevant … because the sphere can encompass both the ceiling and the floor. The spell is instantaneous so that the person did not move when the meteor arrived. Unless they react to the use of a spell to clear themselves, which I suppose is one of the reasons why the target is a point and not a creature . Another is that you can use it on objects. You can not magic missile or eldritch explosion a door but you can meteor swarm he. (Does this really need to be said?)
But physics …
If you are a strict adept of Rules as Written, or even if you are not, the role of a DM is to make sense of the rules in their context. Find a flavor or effect that makes game mechanics work for understanding the surrounding environment and physics. Thus, these meteors already have an inertia from where they are evoked, it is larger than the inverted gravity field, or they have approached the ground so as to collapse. "up" to the characters. The "physics" is not a good reason to lose a user, an NPC or a PC, a level 9 resource for nothing … However …
Yes reverse gravity is already up and meteor swarm is launched – no, I'm not going to let a 7th level spell change a 9th level cast for no good reason, because I think the physics of our world should apply to a world where fiery spheres may just show up, a person waving their arms saying words can reverse gravity, a pretty expensive gem can be used to bring back someone from death, and dragons are a real threat to the local trade … D & D is a simulation , and our description of what happens as a result of mechanics is what makes something credible or not in the world.
Rules as cool
Rules are not everything. If a PC prepares a casting of reverse gravity with a trigger of meteor swarm, it's smart enough. And the order can make a narrative to why the "physics" works and rewards the player for his creativity and his risk of losing a level 7 slot if meteor swarm It's not a casting is a perfectly acceptable narrative tool. Do not use an NPC but allow a PC to do it once is not a problem. That said, they will have to fall more than 85 feet to get away – which will still cause huge damage.