Most NPCs use a flat-basic stat block in lieu of character classes. Please observe the Diviner, a 15th level caster, from Volo’s Guide. This Diviner wizard has (1) class feature, the daily use of ONE ‘Portent’ ability, similar to the PC class ability:
Portent (Recharges after the Diviner Casts a Divination Spell of 1st Level or Higher). When the diviner or a creature it can see makes an attack roll, a saving throw, or an ability check, the diviner can roll a d20 and choose to use this roll in place of the attack roll, saving throw, or ability check.
In contrast with the PC’s Diviner sub-class, NPC wizards can ‘recharge’ this Portent-ability after the use of any spell from their Divination spell-list. Handy. Why?
Explanation on relevance: PCs tend to lack Legendary Resistances and equivalents. Such a Diviner could modify any save or suck spell or situation. Say this wizard observes a PC group against a Beholder, Medusa or Dragon, they need only cast a single divination spell to change dice rolls accordingly. Less need for a Long Rest. Logically, these wizards (of 18+ intelligence) would want as many (cheap) divination spell slots as possible.
Thus, such a wizard would seek to restore spell slots via things like a Pearl of Power. As the magic item list in 5e is extensive, let us focus on spell scrolls. These magic items are relatively easy to make (1st level spell-scrolls are ‘common’ magic items) and seem to approximate a wizard casting their own spell.
If it is relevant, the answer below can include spell scrolls made specifically by this Diviner-wizard themselves &/or those made by other caster-enchanter-scribes. Perhaps it makes a difference if they are casting their ‘own’ spell or not?
If possible, i would be thankful if the answer could also include the infamous Rings or Ioun Stones of Spell Storing, but only if this does not incur the wrath of Stack Exchange Mods. Perhaps it makes a difference if they wizard is regaining their ‘own’ spell via some external source?
Question Specific & Detailed: Can the NPC ‘Divination’ wizard (from Volo’s Guide) restore their daily Portent ability by casting a divination-type spell from a spell scroll magical item – or can this Portent-reuse only be gained via memory-slot spell casting?
Question Simpler: NPC-Volo Wizard-Diviner tries ‘divine spell-scroll’ to restore portent. Works? Yeash? Nope? If ‘nope’, what DOES work? Anything?
Still Simpler – Can a smart NPC-Diviner exploit their 1/day Portent-recharge with a magic item?
So Simple Wize guy so dat, wot?
My thanks in advance.