I’ve heard this phrase a few times in game desing- “Spell in a Box”. Might not be a great item to repeat a ton of times, but how about making one one time?
Spell in a Box
Rare
Magical masters often tire of their servants failing them time and time again. This box is the result. Any spellcaster may cast any spell into a Spell in a Box paying all costs at the time of the spells casting. The spell remains active for a number of days equal to the spells level. At anytime before the spell dissipates, anyone can use the Spell in a Box as an action to cast the spell. When the spell is cast from the box, the spell uses original casters proficiency, ability modifier, and other bonuses to cast the spell, but the creature using the Spell in a Box may determine the effects, range, targets, and any other choices made when the spell is cast.
Thoughts?
Throat Punch Games 
Interesting. But of course such a spell could also theoretically be contained within any closed container and some spell-casters might very well seek to design an artifact or device that can long preserve a spell, even creating spells that hermetically seal a spell within such a container where it can later be broken open for spell release.
Then again such a magically sealed box might contain multiple spells which can be triggered to discharge simultaneously (a sort of Pandora’s box of spells) or in sequence, or by simply hyper-amplifying one spell out of the lot..
If you have a wizard with multiple of a single rare item, that wizard is scary indeed! That could be a fun way to end a campaign.
Reblogged this on Tome and Tomb and commented:
Lot of potential here for expansion and variation.