Keys

The Keys that you find (and lose) in MirrorMoon are not literal keys, as in open a door or start your car, but metaphorical keys, as in "the key to understanding such-and-such." Keys are objects that you will find on most planets, sitting on pedestals in Buildings. Most keys will attach themselves to your Device, granting it some sort of ability. Exceptions include the Orbs, which signal the "solving" of a Side B planet.

Pyramid
A red pyramidal object that is found in Tents on some planets.

Barrel
A cylindrical object that looks a bit like a barrel with every other stave removed. On your Device, it looks like the barrel of a rather peculiar gun. So the name is a double-barreled reference. Look for them in Corridors.

Stubby
Much like the Barrel but very short, both in stature and range. Stubby resides beneath Awnings.

Stubby should perhaps be called Little Thumbling, as per the trading card of that name. But then my orderly super-sleuth brain would insist that the Barrel be called Big Thumbling for symmetry's sake. You see the problem, I trust.

Disk
A blue disk-shaped (duh!) object found in Temples on some planets.

Orbs
These are probably not included in the definition of the single in-game use of the term Keys (see Related Achievements below), but they've got the whole building-pedestal thing going so here they are. There's actually just one Orb, that technimagically transmorphs itself before your eyes!

Fractured Orbs, when investigated, re-assemble themselves into Blinding Orbs. Sounds like fun, don't it?

It is, actually, a very pleasant experience—except for the temporary blindness thing— because it signifies the "solving" of a planet. When your sight returns, you may name it whatever you please; let your imagination run wild! (Six letter maximum, all caps.)

Related Achievements

 * The Other Way Round
 * Lose the keys in Side A in a different order