Mind's Eye - A Magic Item

Part wildlife tagging/remote surveillance program and part series of field experiments, the Mind's Eye Project was instituted by the Rigellian Empire* as a means of testing the biological, psychological, and sociological effects of high-level magic use on humans. (It also doubles as a handy spy network should the surveilled population get rowdy.) Just find an isolated world infested with humanity,** implant some pre-selected individuals*** with "Mind's Eye" devices, then sit back and collect your data.

Outside of the human body, a Mind's Eye looks like a silver lozenge inscribed with the alchemical symbols for "digestion," "projection," and "the Philosopher's Stone" inscribed in gold. When swallowed, the nanomachines which make up the lozenge are triggered by the subject's stomach acid to separate and travel through the bloodstream to the brain, where they reform into a shape resembling a miniature goat's eyeball rooted directly to the visual cortex and connected to the rest of the brain by an extensive network of neural filaments. This process takes d6-1 turns, with a result of 0 meaning it takes d10 seconds instead. Upon completion, the effects listed below manifest in the subject.

If removed from the brain, the eyeball-like mass will reshape itself into its lozenge form over the course of about ten seconds, at which point it can be installed in another host. Mind's Eyes are almost never found in their lozenge state "in the wild," but rather in the brains of the most powerful and ambitious wizards in the land. This is presumably the origin of the stereotype that sorcerers are all brain-eating cannibals.

In it's lozenge state, a Mind's Eye is about as resistant to damage as steel, although it can be "tricked" into separating into a swarm of nanomachines by exposing it to stomach acid outside of a living human, at which point it becomes vulnerable to a variety of other caustic substances, extreme heat or cold, or even simple dilution and separation of the nanomachines to the point that they lose wireless communication with each other and shut down. If attacked directly in its eye-like state, a Mind's Eye has 8 HP and regenerates 1 HP every ten minutes. Killing the subject will not damage the Mind's Eye, simply causing it to revert to lozenge mode.

Effects

• Increases a character's spellcasting ability by one level. This is for purposes of spells per day, spell levels that can be cast, and the caster's level for the purposes of spell effects.
• This does NOT increase the character's level in any other way; it does not grant additional HP or better saving throws or a better attack bonus, it does not change the character's current XP or the amount required for the next level, and it does not allow the character to survive an extra level's worth of being level drained.
• This DOES allow characters to exceed any normal level cap or XP limit for purposes of spellcasting. E.g. A ninth level Magic-User with one Mind's Eye can memorize and cast spells as if they were a tenth level Magic-User, even if ninth level is usually the maximum achievable level in your game.
• This DOES allow members of other character classes and even level 0 characters to memorize and cast spells. E.g. A fourth level Fighter with one Mind's Eye can memorize and cast spells as if they were a first level Magic-User.
• Any character with at least one Mind's Eye can cast spells from scrolls, wands, and staves.
• A human character can only use up to 10 Mind's Eyes at once. Attempting to install 11 or more simultaneously is instantly and invariably fatal to humans.
• Naturally, the referee is free to reduce this amount if desired. E.g. If I were running BX D&D and I had set a level cap of 9 for Magic-Users, I would probably limit the simultaneous use of Mind's Eyes to 5 because the Expert Set only lists the class' level progression up to 14.
• Anything seen by the subject is transmitted to a recording device possessed by the Rigellian Empire, on which it can be played back and otherwise manipulated like standard video footage (albeit in binocular form).
• The current generation of Mind's Eye technology is susceptible to a series of glitches which cause certain visual information to be redirected only to the installed Mind's Eye(s) and not the perception of the subject. For each Mind's Eye installed, a character must succeed on a saving throw vs. magical device or else lose the ability to see one of the following randomly-determined sights: 

1. Random color - Seen as gray instead.
1. Red
2. Orange
3. Yellow
4. Green
5. Cyan/Light Blue
6. Indigo/Dark Blue
7. Purple
8. Violet-Red colors (Magenta, Rose, etc.)
2. Light brighter than 2000 lux - Seen as painful white glare.
3. Light dimmer than 1 lux - Seen as pure blackness.
4. Right angles that take up more than 25% of your field of view - Seen as drastically warped to become acute or obtuse to random degrees.
5. Distances across open air or empty space more than 30 feet across - Seen as being concealed by fog.
6. Motion - Seen as a low-FPS series of still images.

*Or the mysterious otherworldly being(s) of the referee's choice, naturally.

**One can scarcely generate antimatter without blowing up a world that's absolutely overrun with Homo sapiens, and they're just smart enough to cast spells, so they make perfect test subjects.

***As determined by the variables of the specific experiment, and possibly the bureaucratic whims of the researchers' bosses, or the irrational whims of the researchers themselves if they're not very objective.