Before we begin, lets read what minor illusion does

• You create a sound or an image of an object within range that lasts for the duration. The illusion also ends if you dismiss it as an action or cast this spell again.
  If you create a sound, its volume can range from a whisper to a scream. It can be your voice, someone else’s voice, a lion’s roar, a beating of drums, or any other sound you choose. The sound continues unabated throughout the duration, or you can make discrete sounds at different times before the spell ends.
  If you create an image of an object—such as a chair, muddy footprints, or a small chest—it must be no larger than a 5-foot cube. The image can’t create sound, light, smell, or any other sensory effect. Physical interaction with the image reveals it to be an illusion, because things can pass through it.
  If a creature uses its action to examine the sound or image, the creature can determine that it is an illusion with a successful Intelligence (Investigation) check against your spell save DC. If a creature discerns the illusion for what it is, the illusion becomes faint to the creature.

The great thing about this spell, as with many great spells, is its open-endedness.

Lets cut to the chase, Minor illusion can create an image of anything you want as long as you describe it, and there’s no requirements for us to know these images.

Want a fully detailed map of the town of bingletong, a place introduced 5 seconds ago? You can have it. Would you like to see the entire layout of the BBEG’s hideout? the spell minor illusion can make it happen. We can minor illusion spellbook pages and scribe them. We can minor illusion “The enemy we will next fight” and see what’s ahead, heck, the next 100 enemies we will next fight.

Immunity to divination inside a private sanctum inside an antimagic field inside a private demi-plane? Sucks to suck, minor illusion, not being of the divination school nor needing direct access to the place it can “see” anyway, minor illusion still works. Minor illusion can also tell you the exact tone needed on the tuning fork used for that demiplane. (as a side note, this is a counter to GITM, as you can learn the true names of the chwingas attuned to GITM in a nigh-uncounterable way, then summon them out of it). We can also say “an image of X with its statistics cleanly laid out” to gain its statblock.

Omniscience grasped

With minor illusion, any time you need to ‘know’ anything, it is within your grasp. Intrigue plots? deleted. Can’t find scrolls or spell books? too bad, I have access to a theoretical infinity of spells to scribe at any given moment I choose. Minor illusion is hands down the most powerful divinining tool in the game. If we need to add even more divining power to ourselves, take magic mouth. Magic mouth can be set to trigger given a truthful image has been seen, allowing us to have 100% certainty of our minor illusions ultimate reality. (we might be able to do this with another minor illusion, but the first one disappears and it could be slightly annoying to get right)

I don’t think I need to continue to list points where this is useful, any time you want to ‘know a thing’, you can now.

A lot of this tech is theoretically possible with prestidigitation’s “sensory effect” as well, but this is a lot clearer, easier to use, and has other upsides.

All knowledge is yours, friends. should you have the diligence to gather it.