260.) Flask of Shadows
This erlenmeyer flask is filled with wispy black material from the Plane of Shadows. When unstoppered and used as a focus during spellcasting it allows [shadow] spells (and related abilities) to be cast while on planes disconnected from the Plane of Shadow. It contains enough material for 50 such uses, but if brought back to the Material Plane and unstoppered it will refill itself at a rate of one charge per day (or one charge per minute if brought to the Plane of Shadow). If left unstoppered on a plane disconnected from [Shadow] it will leak out at a rate of one charge per minute. If used on the Material Plane or another plane connected to the Plane of Shadows (including the Plane of Shadows itself) it makes [shadow] spells more real, to a maximum of 95% (multiple charges may not be used for a single casting; the percentage cap is for the purposes of if it is combined with other shadow magic boosting items or effects)

Moderate Illusion[shadow]; CL 9; Prerequisites Craft Wondrous Item Greater Shadow Conjuration or Greater Shadow Evocation or Shades; Price 42000gp

(based on cl9 spell level 5 using wall of force, which hedges out antimagic field, as a benchmark. Since it adds a component, subtract the cost of a component removing metamagic rod. Price seems a bit steep so no price hike for the charges recharging and add the boost if on the material plane