Orb of Magic Concentration
Aura: Generic (Strong)
This palm-sized blue orb appears to be a crystal ball, but emits a blue glow, and tingles in the grasp of or contact with any creature that holds or touches it, regardless of size or scale, as long as that creature can feel.
This powerfully-magic orb attracts the magic weave as if by a magnet, granting its holder incredible power to manipulate it to their will. For the touching creature: all positive (conducive) quantities (such as damage, bonuses, saving DCs, durations, ranges, etc.) for a cast have their effect multiplied by 6 within their full range, and all negative (counterconducive) quantities (such as cooldowns, delays, penalties, etc.) divided by 6. For each range increment (of the full range of the original spell), the factor/quotient decreases by 1, up to a maximum of 5 increments (granting 6 times the range to the spell with "normal" effect at the fringe). A range of "Self" or "Touch" implies an increment of 0 (there is no range increase). This effect is unconditional, not "at will", for any creature touching the orb.
For creatures which have natural spell-like or supernatural abilities, the orb affects those casts or uses as well. [Supernatural abilities are abilities predicated on the existence of magic--they'd be ineffective in Antimagic Field, for example. Breath weapons and metallic dragon's shape changing might be considered supernatural, as in 3.5e; 5e moved to "explicitly magical" only in the description, and drops breath weapons to effectively "extraordinary" (non-magical), but see the discussion in the Leaded Restraint template (I still usually treat it as magical).]
The orb's manipulation of the weave is not without cost. Whenever a touching creature casts a spell, regardless of whether or not it uses the effect above: unconditionally roll a magic surge or, at the DM's discretion, a powerful magic effect of their choice may be substituted, usually related to the spell just cast.
The orb is hard, having an AC of 17 and an HP of 15; if it is destroyed, roll 2d6 magic surges with no particular caster and create an explosion of 10d10 force damage centered on where the orb previously was intact, in that order.
Creating such an orb takes a full week of constant spellcasting on a crystal ball focus at a rate of one 1-level spell slot per minute. Because creatures often need to sleep and run out of spell slots, this often requires a large team of shift casters.
Per Detect Magic, this orb has a strong aura, but no particular school affiliation.
The effect of having multiple such orbs does not stack; the weave can only be warped so much.
This is the first magic item I ever created. As such, it's not particularly balanced. If you don't want seriously powerful game breaking (such as 1400 damage from a single Animate Objects cast, dozens of magic missiles doing hundreds of damage, etc.), don't put this item in--or at least use it sparingly.
If you're going to use it anyway, perhaps don't use a giant surge table that also includes, amongst other fun things, Wish. (Or hope that someone gets supernova'd.)
It's been suggested to me that a fair balance for its power is to multiply the casting time accordingly. I leave this to someone else to playtest.
As an unrelenting powergamer, this is one of Froebelius' favorite items; him and an orb go together like a hot dog and a bun.
As the first item, this item set the template for all other items I would prepare. I'm happy with the repleteness of its structure (physical description, mechanical description, statistics (like HP), creation, Detect Magic properties, effect of cardinality), and, indeed, virtually all the other items were written using this structure as a template. I haven't added any new parts since (though the mechanics have only minorly changed--mostly to clarify "orbing" supernatural effects, like Faisal's lightning breath weapon in C2--but see also the discussion of Crawford's ruling in the Leaded Restraint template).