With illusory reality and the 6th level spell Major image, a 14th level wizard can create any object with following limitations.
- The object can’t deal damage or otherwise directly harm anyone. This can be an advantage, though.
- The object is inanimate.
- The object is non-magical.
- You have to use a bonus action every minute to keep it real.
- The object is visible, maybe.
- The illusion is placed within 120 feet of the wizard.
- Maximum size is a 20 feet cube.
Things that are not limitations.
- The object can indirectly harm someone.
- You can make an object real after a period of it being an illusion.
- You do not need to see or be near the object to make it real.
- You do not need to obey gravity when placing the illusion.
- You can move any distance away from the illusion after being placed.
- You can change the nature of a seen illusion (with more than a 9 round duration.) with an action.
- You can move an illusion with 120 feet to somewhere else within 120 feet as an action.
Ambiguous situations.
- It is unknown if a "real" object still counts as an illusion.
- It not specified that the user knows how the object works. Example: You could make a working computer without knowing how they actually work.
- It is not specified that it needs to actually exist. Example: You could make an illusory slade hammer when slade doesn't really exist.
Additional notes.
- You can keep 9 or 10 illusions real at the same time.
- Major Images are reusable, just turn it into whatever you need at the moment, then turn it into a handkerchief or pebble and store it in your pocket when you're not using it.
Uses I have thought up. Obviously dependent on GM, but works in RAW.
- You can create a non-magical panacea, keep it real until you digest it, then change the pile of illusory poop into something else.
- You can create a wall of slade above someone, then make it real to drop down on them and keep them pinned. No direct damage.
- You can make a racing car. If you crash, if the only thing you hit is the car, you won't take damage.
- Hate your enemy racer? Replace his car with an illusion, and then let it become fake again while he's driving it at high speeds.
- You can make can make an adamantine sarcophagus from the head down that keeps the enemy from doing anything but still allows attack on them.
- You can make a layer of metal over the enemy's weapon/claws/mouth that keeps them from hurting anything.
- Make an illusion of a detonating atom bomb, then when you want it detonate, make it real. How useful it is depends on if knockback or radiation are inderect harm or not. At bare minimum it's one hell of a distraction. Oh, and if it can't hurt you, the distracting atom bomb can be made with a minor illusion.
- If you're fighting a horde, you could make an illlusion of a 20x20x20 cube of the toughest known non-magical material around them, with holes to contain them in. Then you can either let them suffocate, or let them go one by one outside to be fought.
- You can make harmless sports equipment, such as actual swords for fencing.
Notes about other spells.
This is only considering 6th level Major Image. I haven't looked carefully at the applications of other spells, mostly because with major image you can just keep nine handkerchiefs in your pocket for when you need it.
Phantasmal forc
However, with an illusion with concentration, you could, say, make a bridge over a gap and then destroy it when an enemy tries to cross.
With Seeming, you can give enemy wizards heavy armor to prevent them from casting spells. You can make the illusion on any number of enemy spellcasters, but how many are real is much lower.
Silent Image and Minor Illusion are cheap ways to do it if you can't get a major image right now.
Do you guys have any other ideas?
Also, while I'm thinking of it, could Seeming make a creature invisible, possibly only with a one foot tall one?
And would a Seeming of a bag over someone's head prevent them from seeing, even without Illusory Reality?
And now that I think about it, Seeming doesn't say how large the clothing and equipment must be, only how much shorter or taller the person themself is. Could you use this to make a "real" fifty foot tall hat?