It is often hard to create magic items strange or original enough to surprise your players.
So here is a tip to get there, while restoring the incomprehensible side of magic : naming the object before describing it! Therefore, we can ask us : how can we name well a magic item ?
And the answer is: rely upon abstruse and cryptic words...
Naming a magic item :
Step 1 : roll a d10.
1. [Name]'s [Adjective] [Noun]
2. [Adjective] [Noun]
3. [Adjective] [Noun] of [Effect]
4. [Adjective] [Adjective] [Noun]
5. [Name]'s [Adjective] [Noun] of [Effect]
6. [Adjective] [Noun] of [Adjective] [Effect]
7. [Name]'s [Adjective] [Noun] of [Adjective] [Effect]
8. [Adjective] [Adjective] [Noun] of [Effect]
9. [Adjective] [Noun] of [Effect] and [Effect]
10. [Noun] of [Effect] and [Adjective] [Effect]
Step 2 : Choose or randomly determine each element of the name so that it is disturbing or difficult to understand.
Step 3 : Deduct / invent the history and the properties of the magic item based on its name.
Thurgal's Acescent Potion of Evanescence is a suntail liquid that looks harmless as you do not drink it. If one identifies it magically, it seems to be a potion of teleportation. However, if you ingest it, it immediately turns in acid (1d6 damage per round, no saving throw) and makes you invisible (no saving throw) !
Thurgal was a sorcerer and a courtier who wanted to poison the Undying Sultan of Aarthal. To do this, he created a particularly vicious acid with many interesting properties. Unfortunately, he was captured before committing his crime and quartered in the public square. It is said that recipe was lost ... but is this really the case?
Nothing prevents you to do so with unique creatures and spells !